maths,,

1.two pipes A and B are joined to a waer tank.To completely fill the water tank with water ,pipe A alone takes 9 hours and pipe Balone takes 12 hours.Suppose the capacity of the water tank is x m3.
a)express the respective amounts of water filled by pipe A and pipe Beach hour in terms of x.
b)if pipe A and pipe B are used simultaneously to fill the water tank with water, there is 70m3 of water in the tank after two hours.Find the capacity of the water tank.