0.24×1.2×150
=(0.24×30)×(1.2×5)
=7.2×6
=43.2
0.8×0.9÷0.8×0.9
=(0.8÷0.8)×(0.9×0.9)
=1×0.81
=0.81
9.9×4.3
=10×4.3-0.1×4.3
=43-0.43
=42.57
8.12×98+8.12×2
=8.12×(98+2)
=8.12×100
=812
6.4×（0.125+12.5）
=0.8×8×（0.125+12.5）
=0.8×（8×0.125+8×12.5）
=0.8×(1+100)
=0.8×1+0.8×100
=0.8+80
=80.8
4.2×75÷25
=4.2×(75÷25)
=4.2×3
=12.6