First, you eat the 5 types each, which only leaves for 8 more. So the top of the would be (8+5-1), for the choose part that means there 1 less type of pizza to choose from which makes the equation
[tex]\binom{8+5-1}{5-1}=\binom{12}{4}[/tex][tex]\binom{12}{4}=\frac{12!}{4!(12-4)!}=\frac{12\cdot10\cdot11\cdot10\cdot9}{4\cdot3\cdot2\cdot1}=495[/tex]This means that there are 495 ways you can do this.