（1）20.9+10.2÷（5.2-3.5）

=20.9+10.2÷1.7

=20.9+6

=26.9

（2）9.4×[1.28-（1.54-0.31）]

=9.4×[1.28-1.23]

=9.4×0.05

=0.47

（3）10.64+7.65×2.4+11.76

=10.64+18.36+11.76

=（10.64+18.36）+11.76

=29+11.76

=40.76

（4）15.52-4.3-5.7

=15.52-（4.3+5.7）

=15.52-10

=5.52

（5）9.83×（3.8-2.3）+1.5×6.17

=9.83×1.5+9.255

=14.745+9.255

=24

（6）[（6.1-4.6）÷0.8-1]×0.4

=[1.5÷0.8-1]×0.4

=[1.875-1]×0.4

=0.875×0.4

=0.35