计算下面各题，能简算的用简便方法计算。 18.9×9.9 12.5×8.94×0.8 7.4×0.5+7.4÷0.5 4

18.9×9.9
=18.9×（10-0.1）
=189-1.89
=187.11 12.5×8.94×0.8
=（12.5×0.8）×8.94
=10×8.94
=89.4 7.4×0.5+7.4÷0.5
=7.4×（0.5+2）
=7.4×2.5
=18.5
4.92÷2.4
=2.05 6.8×32+32×3.2
=32×（6.8+3.2）
=320 （8.1-5.6）÷0.8+7.75
=2.5÷0.8+7.75
=10.875
5.92×2.5
=14.8 5.6×（12.5-8.5÷0.85）
=5.6×2.5
=5.6÷0.4
=14 3.5×[13-（3.12+5.28）]
=3.5×（13-8.4）
=3.5×4.6
=16.1