Consider this reaction:
4NH3 + 5O2 --> 4NO + 6H2O

If you start with 4 moles of NH3 and 3 moles of O2, then:

How many moles of NO can be formed?

How many moles of H2O can be formed?

3/5*4 = 2.4 moles of NO
3/5*6 = 3.6 moles of H2O