ответ: 15 целых 3/7
1 5/7 * 1 3/4 * 5 1/7 = 15 3/7
1) 1 5/7 * 1 3/4 = ((7*1+5)/7) + ((4*1+3)/4) = 12/7 * 7/4 = 3
2) 3 * 5 1/7 = 3 * ((7*5+1)/7) = 3 * 36/7 = 108/7 = 15 3/7
