The reaction is: 2NH3 + H2SO4 -----> (NH4)2SO4 it tells us that 2 moles of ammonia yields 1 mol of Ammonium sulfate. So we just need to state that: 2 moles NH3 - 1 mol (NH4)2SO4 30 moles NH3 - x x = (30) (1) / 2 = 15 moles of (NH4)2SO4
Hope this helps! And remember if it does give me a like, please and thank you!