2/9-6/13×2/9 =2/9x(1-6/13) =2/9x7/13 =12/117 36×(17/18-2/9) =36x17/18-36x2/9 =34-8 =26 4/13×4/7-3/7×4/13 =4/13x(4/7-3/7) =4/13x1/7 =4/91