0.22=
6.8+1.28=
0.5÷0.25=
50×30%=
1﹣1÷7=
6÷=
×24=
2008﹣199=
+=
2.5×0.7×0.4=
①x+x=42
②=
①1.8+3.84÷(15﹣12.6)
②
③
④0.4×80×2.5×0.125