5.08*1.1=5.08*(1+0.1)=5.08+0.508=5.588;4.9*99+4.9=4.9*(99+1)=4.9*100=490;(19.3-6.8)/4/2.5=(19.3-6.8)/10=1.93-0.68=1.25;0.9/3.05/0.9*3.05=0.9*3.05/(0.9*3.05)=1;