简便计算: 99%+91x(2/13-1/7)=0.99+14-13=1.99 .
99%+91x(2/13-1/7) =99%+91×2/13-91×1/7=99%+14-13=1.99
99%+91x(2/13-1/7)=0.99+14-13=0.99+1=1.99