Pipes and Cistern - General Questions

Pipes A and B can fill a tank in 14 and 27 minutes, and pipe C can empty it in 22 minutes. If all three are opened together, how long will it take to fill the tank?

Two pipes A and B can fill a tank in 18 hours and 12 hours respectively. If both are opened together, how long will they take to fill the tank?

A pipe can fill a tank in 3 hours and another pipe can empty it in 22 hours. If both are opened together, in how much time will the tank be filled?

A pipe can fill a tank in 10 hours and another pipe can empty it in 23 hours. If both are opened together, in how much time will the tank be filled?

Two pipes A and B can fill a tank in 7 hours and 20 hours respectively. If both are opened together, how long will they take to fill the tank?