①x∶12=×2.8
②=
③∶=x∶15
523﹣23×7
4.97+6.38+5.03﹣4.38
60×()
×3.2+5.6×0.5+1.2×50%
()÷
∶x= :
= ﹣0.25= 0÷5=
= 5.4×= 80×0.7=
10
8
5
1
3
2
6