Alright, lets gets started.
If water enters through a pipe alone, swimming pool can be filled in 12 hr.
Or say, in 12 hrs, swimming pool can be filled with help of pipe.
It means in 1 hr, the part of swimming pool filled = (For pipe only)
Similarly, with hose only, , in 1 hr, the part of swimming pool filled =
So, water is coming from both, pipe and hose , then in 1 hr, the part of pool filled will be =
Suppose in x hrs, with both supplies, pipe and hose, pool is filled.
Means
making common denominator
Flipping
Means 8.57 hrs : Answer
Hope it will help :)