5x-5=40
2.5x+2.5=5
2(x+0.8)=2.2
①0.42×15=
②5.2×0.8=
③1.37×0.21≈(得数保留一位小数)
④2.16×8=
4.8÷2=
0.35÷5=
0.6×0.5=
20×0.4=
100×0.039=
1.2÷3=
0.2×0.3=
1.1÷10=