7.4-0.15*2.8要简便 21.36/0.8-12.9要简便 4*（1.5+0.25）要简便
问题描述：
7.4-0.15*2.8要简便 21.36/0.8-12.9要简便 4*（1.5+0.25）要简便
答
7.4-0.15*2.8=7.4-0.15*(3-0.2)=7.4-(0.15*3+0.15*0.2)=7.4-(0.45+0.03)=6.9821.36/0.8-12.9=(22-0.64)/0.8-(13-0.1)=22/0.8-0.64/0.8-(13-0.1)=27.5-0.8-13-0.1=13.64*(1.5+0.25)=4*1.5=0.25*4=6+1=7