Chemistry help please? PLEASE explain your answers, thanks!?

Hi---Could someone please help me??? I am struggling! PLEASE explain your answers so I can follow you. Thanks to all. All help is greatly appreciated! :)

Calculate each of the following:

(a)Mass of % of H in ammonium bicarbonate
(b) Mass of % of O in sodium dihydrogen phosphate heptahydrate
2 answers 2