3x-= x+= +-x=
= = = =
1-0.001= 1÷4= 0.9+0.1÷0.1=
9÷0.6= 12×0.05= 1.4-1.4÷7=
2.5×4×0.8= 3.6÷0.7≈ (得数保留一位小数)