You'll need Avogadro's number for this. NH3 has 1 Nitrogen and 2 Hydrogen. You'll multiply the molar mass of each times Avogadro's number. So:
molar mass N x 6.022x10^23 x 1 Nitrogen= total A
Molar mass H x 6.022x10^23 x 2 Hydrogen= total B
Add total A+B = your answer
I don't have a calculator or periodic table but if you plug in the numbers you'll get your answer. Hope it helps.
