(0.63+0.37)*8.7=8.7
原式=0.63×8.7+8.7×0.37=8.7×(0.63+0.37)=8.7×1=8.7
63%×8.7+0.87×3.7 =0.63×0.87×10+0.87×3.7=(6.3+3.7)×0.87=10×0.87=8.7
原式=8.7*(0.63+0.37)=8.7