1、2.6×99＋2.6 =26*（99+1）=26*100=2600
2、21÷（1/3+2/5）÷9/11
=21÷（11/15）÷9/11
=21*15/11*11/9
=21*15*1/9
=7*5
=35
3、18.5-（5.6+4.8）/1.3
=18.5-10.4/1.3
18.5-8=10.5