Answer:
34.5 meters square.
Explanation:
Walls: 4 x 5 meters
Roof: 5 x 5 meters
20 x 0.5 = 10
25 x 1.5 = 37.5
10 + 37.5 = 47.5
There is a window and a door she doesn't need to wash that takes up some of that space. The window takes up 4 square meters and the door takes up 9 square meters. So, there is 13 square meters she will not wash (4+9=13).
We subtract what she won't wash from our original number of 47.5.
47.5 - 13 = 34.5