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