arithmetic - two pipes a and b together can fill a tank in 8 hours had they been opened separately then b would have taken 12 hours more than a to fill the tank how much time will be taken by a to fill the tank separately - skillgun

Solution: Let the tank be filled by pipe A alone in x hrs.
Then, pipe B will fill it in (x+12) hrs.
.'. 1/x + 1/(x+12) = 1/8
=> 8(x+12+x) = x(x+12)
=> x^2 -12x -96 = 0
=> x = 12.