The length of a rectangle is 8 cm more than 3 times its width. the perimeter of the rectangle is 64 cm. show the equation that would be used to find the dimensions of the rectangle. let w = the width. then 3w = length + 8. so the equation is 64 = 2(3w – 8) + 2w. let w = the width. then 3w + 8 = length. so the equation is 64 = 2(3w + 8) + 2w. 64 = 2(3w + 8) + 2w let w = the width. then 3(w + 8) = length. so the equation is 64 = 2(3(w + 8)) + 2w. let w = the width. then 3w + 8 = length. so the equation is 64 = (3w + 8) w.