Let the length be x and the width be y.
Since the length is 9cm less than 4 times the width, it can equal to:
x = 4y-9
The area would be:
xy = 28
But since we have the first equation, we can substitute it into the second:
4y-9*y = 28
4y^2 - 9y = 28
4y^2 - 9y - 28 = 0
Factorize this to make it:
(x-4)(4x+7) = 0
x= 4 or x = -7/4
Since the dimensions cannot be negative, the width is 4cm, and the length would is 7cm.
