①(3618÷18-145)×20
②6÷ - ÷6
③(21+ )× +
④ ×[ ÷( - )]
⑤3.5×98+35×0.2
3.1+0.4= += 640÷16= ×3×4=
10÷= ×= 2.4×= 25×40%=