Answer:
2 units
Explanation:
Area = Length × Width of a rectangle
If Length = L
Width = L-4
So 12 units = L×(L-4)
12 = L^2 -4L
L^2 -4L -12=0
Simplify this equation
L^2 + 2L -6L -12 = 0
L( L+2) - 6(L+2) = 0
(L+2) (L-6) = 0
L+2 =0 Or L-6=0
L=-2 Or L= +6
But L can't take a negative value
therefore L= 6
Now if we substitute and check,
L× (L-4) = 6×2=12 units
width = 6-4 =2 units