7.2÷0.9+2.1
=8+2.1
=10.1
27.3÷1.2－8.8
=27.3÷0.3÷4-8.8
=22.75-8.8
=13.95
9.6－2.4×3.5
=2.4×4－2.4×3.5
=2.4×（4-3.5）
=2.4×0.5
=2.4÷2
=1.2第一个怎么不用简便运算？7.2÷0.9+2.1 =(7.2×10)÷（0.9×10）+2.1=72÷9+2.1=8+2.1=10.1