6.72÷2.5÷0.4 5.4×101
9.8÷(0.23+1.3×0.2) [(6.1-4.6)×0.8]÷0.4
①x-= ②(-)-x=
1.2×2= 20×33%= 31×299≈
0.4÷8= + = 631÷9≈