M NH4NO3= 14+4*1+14+3*16=80g/mol
In 80g NH4NO3...................28gN
8 g NH4NO3 ...................x
x=8*28/ 80=2,8 gN
M NH4Cl=14+4*1+35,5=53,5 g/mol
In 53,5 gNH4Cl...................14gN
52,5gNH4Cl....................a
a= 52,5*14/ 53,5=13,73g N
M (NH4)3PO4= 14*3+4*1*3+31+4*16=149 g/mol
In 149g (NH4)3PO4....................(3*14)g N
1,49g(NH4)3PO4...................b g N
b=1,49*42/ 149=0,42gN
