Question

Two pipes can fill a tank in 15 hours and
20 hours respectively, while the third
pipes can empty it in 30 hours. If all the
pipes are opened simultaneously, the
empty tank will be filled in
1) 10 hours 2) 12 hours 3) 15 hours
4) 151 hours 5) 14 hours​

Answer 1

15 hours

sorry I can't conform 100%

I hope this is right