三又五分之三乘二十五又五分之二加37.9乘六又五分之二=3又3/5×25又2/5+37.9×6又2/5=3.6×（19+6.4）+37.9×6.4=3.6×6.4+3.6×19+37.9×6.4=6.4×（3.6+37.9）+3.6×（20-1）=6.4×41.5+3.6×（20-1）=6.4×（40+1...