51.2*23.4+35.9*48.8=（50+1.2）* 23.4+（23.4+12.5）*（50 - 1.2）=（50+1.2）*23.4+（50-1.2）*23.4+12.5 *（50 - 1.2)=100*23.4+12.5*(50-1.2)=2340+12.5 * 50 - 12.5*1.2=2340+625-15=2950