the length of a rectangle is twice it's width. if it's length is decreased by 3 cm , and it's width is increased by 5 cm the result will be a square , then the perimeter of this rectangle will equal ...... cm
L = Length
W = Width
A square has sides of equal length.
In this case :
L - 3 = W + 5
L = W + 5 + 3
L = W + 8
L = 2 W
2 W = W + 8
2 W - W = 8
W = 8 cm
L = 2 W
L = 2 * 8 = 16 cm