You need to set up the problem to solve for X. X = how tall is the tree? Set up your problem in this fashion. Set up the formula then arrange to solve for X. X/9 (shadow of the tree) = 15 (how tall the building is)/6 (shadow of building) X= 15/6 * 9 To get X alone, you need to move 9 to the other side of the equation. multiply by 9 on each side. For X side, this nullifies 9 and gets 9 to the other side. X= 2.5*9 You have divided 15 by 6, now multiply by 9 to get final answer for X X=22.5 meters The tree is 22.5 meters tall.