Here is the question:

In a fixed volume container,6*10(power 23) molecules of a gas exert a pressure of 12N/m2. If 12*10(power 23) molecules of gases were added to a container what would be the pressure?

Using ideal gas law I solved the problem and i got 24N/m2 as the answer. But the answer given is 36N/m2. Can some one justify it?