Grade 8 math problem 36 / (1 + 25%) x-18 / x = 6

Grade 8 math problem 36 / (1 + 25%) x-18 / x = 6

Multiply both sides by 1.25x to get 36-22.5 = 7.5x;
So 13.5 = 7.5x, so x = 1.8