Ответ:

а) SO₂: m(S):m(O) = 32:(2·16) = 1:1.

б) P₂O₅: m(P):m(O) = (2·31):(5·16) = 62:80 = 31:40.

в) CO₂: m(C):m(O) = 12:(2·16) = 3:8.