Ответ:а) \(7+5.31+9+13.49=34.8\); б) \(62.7+8.31+5.79+0.07=76.87\).а) \(8.31-(4.29+3.721)=8.31-8.011=0.299\); б) \((8.21+9.73)-0.001=17.94-0.001=17.939\).