Pipes A and B, when working together, can fill an empty tank in 8 hours. If B is stopped after 2 hours, it will take a total of 11 hrs to fill the tank. How long would it take A to fill the empty tank alone?
In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?