Вычтслите произвкдение 13/10*100/39; 7/8*4/35*10/9; 42/56*16/5*15/36; 6/7*5/6; 13/15*45/26; 5/7*7/13*13/18; 101/102*102/103*103/104; 6/7*7/6.