急求20道小学六年级奥数计算题!高悬赏100分啊!

14/15X8 2/25X126 35X11/36 73X74/75 1/17X4/9+5/17X1/9 1/2+1/4+1/8+...1/256 2/3+2/9+2/27+2/81+2/243 9.9+99.6+999.6+9999.6+99999.6 6X7/12-9/20X6+11/30X6 3/2+5/6-7/1