Question 461531
Let x be how wide the rectangle is. Then 3*x is how long the rectangle is. If a rectangle is a units long and b units wide the a*b is the area of the rectangle. So for this rectangle to decrease the width and longness of the rectangle by 2 cm we must have that
(x-2)*(3x-2) = (x)*(3*x) - 36
3*x*x - 2*x -6*x +4 = x*3*x - 36

-8*x = -40
x = 5

So the width of the rectangle is 5 and the rectangle is 15 cm long.