①0.75x+3×0.8=7.5
② x+ x=3.5
③42: =x:
1.2×0.3= ﹣= 32÷53×0=
0.25÷= 1﹣0.09= +20%=
2380﹣450÷18×48 2.3+3.91÷(22﹣19.7) ÷[(+)×]