Question 275369
(6 / h) + [6 / (h - 9)] = 1


6h - 54 + 6h = h^2 - 9h


0 = h^2 - 21h + 54


0 = (h - 18) (h - 3)


h = 18


h = 3 does not work because 9 less than 3 would be negative time ...