①÷÷20
②××
③÷×
④×÷
×3=
×0.8=
1÷=
0.004+99×0.4%
×25+175×75%
10.25× +2.5%
24×
×9.3+9.3×0.25
÷
2×0.8= 75﹣20= ×12= 42÷=
+= 1.5÷3= 501×100≈ ×0÷=