Answer:
Let's take all factors into consideration first
The door is a rectangle and the area of a rectangle is length times width
Let the width be w
Let the length be l
Equation length × breadth = area
(w+48)w = 3024
w^2 + 48w = 3024
w^2 + 48w - 3024 = 0
w^2 + 84w - 36w - 3024 = 0
w(w + 84) -36 ( w + 84) = 0
(w + 84) (w - 36) = 0
w + 84 = 0 AND w - 36 =0
w = -84 and w = 36
Since width cannot be negative, the right answer is 36
How did I get 84 and 36? Well, I had to factorize 3024 and since 84 times 36 is 3024 and 84 minus 36 is 48, I chose them.