（1）原式=5.68+1.8

                =7.48（2）原式=21.59-5.56

                =16.03

（3）原式=86.74-8.38

                =78.36（4）原式= 45.6- 4.9

                = 40.7

（5）原式=17.41-16

                =1.41（6）原式=8.19+1.97

                =10.16