1/3h - 4(2/3h - 3) = 2/3h - 6
h / 3 - 8h / 3 + 12 = 2h / 3 - 6 <=>2h / 6 - 16h / 6 - 4h / 6 = - 108 / 6<=>-18h / 6 = -108 / 6 <=> -18h = - 108 <=>h = 108 / 16 <=>h = 27 / 4 <=>h = 6.75.