You must follow the proccedure shown below to solve this problem:
You have that the floor of a triangular room has an area of 32 1\2 m² If the triangle altitude is 7 1\2 m. Then, you have:
A=32 1/2 m²=32.5 m²
h=7 1/2 m=7.5 m
Now, you can calculathe b as below:
A=bxh/2
b=Ax2/h
When you substitute the values, you obtain:
b=32.5 m²x2/7.5 m
b=65 m²/7.5 m
b=8.66 m
