I'd honestly go with forty eight.
Assuming the shape of the room is a rectangle :
Area = Width x Length.
Let's call width "w" and length "l" . Now if, the width is 4/5 of the length that means 4/5 times length gives us the width, like this :

As given in the question, area of the rectangle is 320 square feet. And as I said before area of a rectangle can be found by multiplying its length and width.


, we can plug w's value in the previous equation to find "l".

Let's plug "l"s value in the equation.

The length is 20 feet and the width is 16 feet.
I believe that the answer will be 619.4.
Let me know if it works.
Answer:
11
Step-by-step explanation:
8 + 3*(4-3) = 8 + 3*1 = 8+3 =11