74x57十42X74十74＝74X（57十74十1）＝74X122＝9028
74×57+42×74+74=74×(57+42+1)=74×100=7400
74＊57+42＊74+74=74＊（57+42+1）=74＊100=7400
=74x(57+42+1)=74x100=7400
74×57+42×74+74=（57+42+1）×74=100×74=7400
