А) 1/2 * 2/3 = (1*2)/(2*3) = 1/3
б) 6/7 * 5/6 = (6*5)/(7*6) = 5/7
в) 9/10 * 10/11 = (9*10)/(10*11) = 9/11
г) 13/15 * 15/17 = (13*15)/(15*17) = 13/17
д) 14/13/5 * 5/42 = (14*5)/(15*42) = 1/(3*3) = 1/9
е) 13/15 * 45/26 = (13*45)/(15*26) = 3/2 = 1,5
ж) 15/28 * 7/30 = (15*7)/(28*30) = 1/(4*2) = 1/8
з) 35/51 * 17/15 = 7/(3*3) = 7/9