calculate the percentage of nitrogen in the following fertilizer i NH4NO3 ii NH4/2SO4

Answer 1

Let's do apples and oranges. If you had 10 lbs apples and 10 lbs oranges what percent apples do you have. That't 50%, of course, How did you get that. %apples = (lbs apples/total weight in lbs)*100 = (10/20)*100 = 50. So you have a chemistry problem and not apples and oranges BUT it works the same way.
%N = (mass N/molar mass NH4NO3)*100 = ? Don't forget there are 2 N atoms in NH4NO3.
Do (NH4)2SO4 the same way.
Post your work if you get stuck. Don't let the word "chemistry" intimidate you.