Answer:
9
Explanation:
What you do if first you draw your rectangle. You name length as x (as told in the question) and width as x-3 (since the width is 3 feet less). To obtain the area you have to do x × (x-3) because to find area you do length × width right.
So area is x(x-3) and it also tells you that area is 54 there
That's how you get x(x-3)=54
Now to solve it, you have to expand
x(x-3)=54
x²-3x-54 = 0 (you have to factorise this now)
(x+6) or (x-9) = 0
x = -6 or x = 9
As you can see you have two answers there. We have to eliminate the -6 because length can never be negative. The logic is simple, any length you take for example on a ruler (it has to be 0 or above) you can measure 1 feet, 2 feet, even 100 feet but you can't measure less than 0 right?
So the final answer is that x=9 and x represents the length
So length = 9