Let, width = x
Length = x + 4
It is given that, (x+4)(x) = 21
x² + 4x = 21
x² + 4x - 21 = 0
x² - 3x + 7x - 21 = 0
x(x - 3) 7(x - 3) = 0
(x+7)(x-3) = 0
x = -7 or 3
Width (Distance) can't be in negative form, so -7 is rejected.
In short, Your Answer would be 3 meter.
Hope this helps!
