А) C4H6O4
M(C4H6O4)=110 г/моль
w(C4)=48/110*100%=43%
w(H6)=6/110*100%=5%
w(O4)=100%-5%-43%=52%
б) C6H7N
M(C6H7N)=93 г/моль
w(C6)=72/93*100%=77%
w(H7)=7/93*100%=7%
w(N)=100%-77%-7%=16%
в) NaNO3
M(NaNO3)=85 г/моль
w(Na)=23/85*100%=27%
w(N)=14/85*100%=16%
w(O3)=100%-27%-16%=67%