Pipe A can fill the tank in 8 minutes, Pipe B can fill the tank in 16 minutes. Pipe C is an emptying pipe whose efficiency is 33.33% more than the efficiency of pipe B. If all pipes A, B and C opened for 6 minutes and C alone opened and the other two pipes were closed for 3 minutes. Now all the pipes A, B and C fill the whole tank in x minutes. Find the value of x.