The perimeter of the box is two times the length plus two times the width. We know this is 90cm so2(2x + 2) + 2(x-2) = 904x+4+2x-4 = 0-6x = 90x = 15 From there, you can find the length and the width and height by substituting in for x. Lastly, the volume is the product of the three of those and you will have your answer.