先把除法变为乘法原式=1.2×1/3+2.7×1/3+4.2×1/3=（1.2+2.7+4.2）×1/3=2.7
1.2 ÷3+2.7÷3+4.2÷3=(1.2+2.7+4.2)÷3=8.1÷3=2.7
(1.2+2.7+4.2)÷3=8.1÷3=2.7
不会算
8.1÷3
