What if it's leeward on the south side?

Hello, normally the windward side is always on the south side, but what if the leeward side is on the south side? How do you calculate the degrees then?
There is a task that I don't understand, I tried all possibilities but I couldn't get it done

task: given: temperature leeward at 400m 27 degrees

height of the Alps: 3500m

cloud formation at 1500m

wanted: temperature upwind at 300m

The solution is 18 degrees but that's all I get (it always comes out 26/25 degrees)

can anyone help me?

thanks in advance