22×0.75+25×75%-7×0.75=22×0.75+25×0.75-7×0.75=（22+25-7）×0.75=40×0.75=30
22×0、75+25×0，75-7×0，75=(22+25-7)×0，75=30
（22+25-7）*0.7540*0.7530
