Answer:
width = 6
Explanation:
We can think of the width as x and the height as 3x-6. the perimeter formula is (width + height)*2, since we have x as width and 3x-6 as height, we can put it in the formula, which will get you (x + 3x-6)*2 = 36, if we devide both sides by 2, we'll get (x + 3x - 6) = 18, when we simplify it, we will get 4x-6 = 18, which can then be simplified into 4x = 24, which will get you that x = 6
Hope it helped :)