If I'm not wrong, all you have to do is use the distributive property.
We know 20% is 15
and now we find 80%
since 20% x 4 = 80%, we can multiply 15 by 4 to get 80% of 75
15 x 4 = 60
80% of 75 = 60
Answer:
I believe that the area of the green square is 9ft²