√(2h/g) - √[2(h-3)/g] = 0.2
√h - √(h-3) = 0.2 ×√(g/2) = 1/√5
√h = √(h-3) + 1/√5
h = h - 3 + 2√[(h-3)/5] + 1/5
√[(h-3)/5] = 7/5
(h-3)/5 = 49/25
h = 12.8