运用分配律，结合律例如；（2/3+1/6）*6=(2/3)*6+(1/6)*6=5 ( 9/10)*(5/4)*22=( 9/10)*(5/4)*(20+2) =( 9/10)*(5/4)*20+( 9/10)*(5/4)*2 =99/4
