（1）原式=6+0.8

                =6.8

（2）原式=[10.8-（1.26+0.74）]×2.7

                =8.8×2.7

                =23.76

（3）原式=12.5×0.8×4.6

                =46（4）原式=（0.73+0.27）×68.4÷0.01

                =6840