（0.75*42.6-0.574*25+57.4）/3
=[（1-0.25）*42.6-57.4/100*25+57.4]/3
=[（1-0.25）*42.6-57.4(1/100*25-1)]/3
=[（1-0.25）*42.6-57.4*(0.25-1)]/3
=[（1-0.25）*42.6+57.4*(1-0.25)]/3
=[（1-0.25）*(42.6+57.4)]/3
=[（1-0.25）*100]/3
=[0.75*100]/3
=0.75/3*100
=0.25*100
=25