1a. Biết $M_{A} = 1.375*M_{O_{2}}$
=> $M_{A} = 1.375*32$
=> $M_{A} = 44$
=> $M_{X} = 44-(2*16) = 12$
=> X = C (Cacbon)
=> $A = CO_{2}$
1b. Biết $M_{A} = 3.375*M_{O_{2}}$
=> $M_{A} = 3.375*32$
=> $M_{A} = 108$
=> $2M_{X} = 108-(5*16) = 28$
=> X = 14
=> X = N (Nitơ)
=> A = $N_{2}O_{5}$