Question

What is the formula for finding the length? I can’t figure it out.

Answer 1

Sorry, my previous answer was wrong. Here is the new one:

Since we know A=l*w
Therefore, l=A/w
Then, we can use the equations they gave us and divide the area equation by the width equation, which would give us 3x. Therefore, the length would be 3x

Answer 2

the formula is l=a/w so divide your problems and then you will have the missing side lenghth of 3x