Mr(NaOH): Ar(Na)=23
Ar(O)=16
Ar(H)=1
Mr(NaOH)=23+16+1=40
Mr(H₃PO₄): Ar(H)=1*3=3
Ar(P)=31
Ar(O)=16*4=64
Mr(H₃PO₄)=3+31+64=98
Mr(Al(OH)₃): Ar(Al)=27
Ar(O)=16*3=48
Ar(H)=1*3=3
Mr(Al(OH)₃)=27+48+3=78
Mr(HNO₃): Ar(H)=1
Ar(N)=14
Ar(O)=16*3=48
Mr(HNO₃)=1+14+48=63