2.7-a-b=2.7-(+)
6.1×m×n=6.1×(×)
34×x+3.4×y=×(+)
, 1.6×0.131.6,0.27×bb(b>0),4.08×0.114.08÷0.11
①9.1÷0.13÷0.25
②1.8×25+24÷1.5
③(18.6+12.6)÷4