Question

How do I figure the number of atoms in the formula 2(NH4)3PO4?

Answer 1

If you want to know how many atoms are there you must know how much of the compound you have. However, if you are interested in the number of atoms in one molecule:
you have 6N
24H
2P
8 O for a total of 40? Right?

Answer 2

Thanks! That is what I thought, but needed a second.