49.5/9+35.1/7.8 =5.5+4.5=10{2.5-8分之31/（6分之11+0.75）}*17分之30 ={2.5-31/8÷31/12}×30/17={2.5-1.5}×30/17=30/1719.63*99+19.63=19.63×（99+1）=19.63×100=1963（76-105*0.6）*13分10 =（76-63）×10/13...