Why can't C++ add, subtract, divide, or multiply?

Here is the source code:

#include 
#include 


using namespace std;


class Var {
public:
	int roundsUntilTheEnemyComes = 3;
	int player_power = 0;
	int enemy_power = 0;
	int rounds = 0;
	bool bIsDead = 0;
	int Money = 0;
	int towers = 0, soldiers = 0, schools = 0, soldierSchools = 0, archerSchools = 0, archers = 0, walls = 0, goldMines = 0;
};
class Voids {
public:
	static void Enemy() {
		Var v;
		if (v.rounds == 0) {
			v.enemy_power = 50;
		} else if (v.rounds <= 5 && v.rounds != 0) {
			v.enemy_power += 90;
		} else if (v.rounds <= 15 && v.rounds >= 5) {
			v.enemy_power += 150;
		} else if (v.rounds <= 50 && v.rounds >= 15) {
			v.enemy_power *= 2;
		} else if (v.rounds <= 75 && v.rounds >= 50) {
			v.enemy_power *= 5;
		} else if (v.rounds > 75) {
			v.enemy_power *= 10;
		} if (v.player_power > v.enemy_power) {
			v.bIsDead = false;
		} else {
			v.bIsDead = true;
		}
	} static void IsDeadCheck() {
		Var v;
		if (v.bIsDead) {
			cout << "\n \n \n!!!You are dead!!!";
		}
	} static void MainGame() {
		int dec;
		Var v;
		cin >> dec;
		if (dec == 1) {
			if (v.Money >= 50) {
				v.towers++;
				v.player_power += 5 * (v.archers / 2) + (v.soldiers / 2);
				v.Money -= 50;
				cout << "You have " + to_string(v.Money) + "G left. Your power now is " + to_string(v.player_power) + ", and you now have " + to_string(v.towers) + "Towers! \n";
			} else {
				cout << "You don't have enough money to buy a tower! \n";
			}
		} else if (dec == 2) {
			if (v.archerSchools > 0) {
				if (v.Money >= 5) {
					v.archers++;
					v.player_power = v.archers * v.archerSchools;
					v.Money -= 5;
					cout << "You have " + to_string(v.Money) + "G left. Your Power now is " + to_string(v.player_power) + ", and you now have " + to_string(v.archers) + "archers! \n";
				} else {
					cout << "You don't have enough money to buy a tower! \n";
				}
			}
		} else if (dec == 3) {
			if (v.Money >= 50) {
				v.archerSchools++;
				v.player_power++;
				v.Money -= 50;
				schools("archer");
				cout << "You have " + to_string(v.Money) + "G left. Your Power now is " + to_string(v.player_power) + ", and you now have " + to_string(v.archerSchools) + "Schools for Archers! \n";
			} else {
				cout << "You don't have enough money to buy a school for archers! \n";
			}
		} else if (dec == 4) {
			if (v.soldierSchools > 0) {
				if (v.Money >= 5) {
					v.soldiers++;
					v.player_power += 5 * v.soldierSchools;
					v.Money -= 5;
					cout << "You have " + to_string(v.Money) + "G left. Your Power now is " + to_string(v.player_power) + ", and you now have " + to_string(v.soldierSchools) + "schools for soldiers! \n";
				} else {
					cout << "You don't have enough money to buy a soldier! \n";
				}
			} else {
				cout << "You can't make any soldiers without a soldier school! \n";
			}
		} else if (dec == 5) {
			if (v.Money >= 50) {
				v.soldiers++;
				v.soldierSchools++;
				v.Money -= 50;
				v.player_power += 10;
				schools("soldier");
				cout << "You have " + to_string(v.Money) + "G left. Your Power now is " + to_string(v.player_power) + ", and you now have " + to_string(v.archerSchools) + "Schools for Archers! \n";
			} else {
				cout << "You don't have enough money to buy a soldier school! \n";
			}
		} else if (dec == 6) {
			if (v.walls > 4) {
				if (v.Money >= 20) {
					v.walls++;
					v.player_power += 4 * (v.archers + v.soldiers);
					v.Money -= 20;
					cout << "You have " + to_string(v.Money) + "G left. You Power now is " + to_string(v.player_power) + ", and you now have " + to_string(v.walls) + "Walls for you castle! \n";
				} else {
					cout << "You don't have enough money to buy a wall. \n";
				}
			}
		} else if (dec == 7) {
			v.goldMines++;
			v.Money += 25;
			cout << "You bought a Goldmine! \n";
			if (v.rounds <= 1) {
				v.player_power += 50;
				v.Money += 50;
				cout << "You now have " + to_string(v.Money) + "G and you Power is " + to_string(v.player_power) + "! \n";
			}
		} else if (dec == 8) {
			if (v.Money >= 60) {
				v.archers++;
				v.soldiers++;
				v.schools++;
				v.player_power++;
				v.Money -= 60;
				schools("all");
			} else {
				cout << "You don't have enough money to buy a school!";
			}
		}
	} static void schools(string typeOfSchool) {
		Var v;
		if (typeOfSchool == "archer") {
			v.archers++;
		} else if (typeOfSchool == "soldier") {
			v.soldiers++;
		} else if (typeOfSchool == "all") {
			v.soldiers++;
			v.archers++;
		}
	}
};


int main() {
	Voids GameVoids;
	Var v;
	v.roundsUntilTheEnemyComes = 3;
	v.Money = 0;
	v.player_power = 0;
	cout << "!!!Game Start!!! \n";
	while (true) {
		if (v.roundsUntilTheEnemyComes != 0) {
			cout << "What do you want to buy? \n";
			cout << "(1) A Tower | (2) An Archer | (3) An Archer School | (4) A Soldier | (5) A Soldier School | (6) A castle Wall | (7) A Goldmine | (8) A School \n";
			GameVoids.MainGame();
			if (v.archerSchools > 0) {
				v.archers += v.archerSchools;
				v.player_power += v.archerSchools;
			} if (v.soldierSchools > 0) {
				v.soldiers += v.soldierSchools;
				v.player_power += v.soldierSchools;
			} if (v.goldMines > 0) {
				v.Money += 25 + (v.goldMines / 2);
			} if (v.schools > 0) {
				GameVoids.schools("all");
				v.player_power += 2 + v.schools + (v.archerSchools / 2) + (v.soldierSchools / 3);
			}
			v.roundsUntilTheEnemyComes--;
		} else {
			GameVoids.Enemy();
			GameVoids.IsDeadCheck();
			if (v.bIsDead) {
				cout << "\n \n \nThe Power of the Enemy was" + v.enemy_power;
				break;
			} else {
				v.rounds++;
			}
		}
	}


	return 0;
}