1/51 и 1/68 = 1/(3*17) и 1/(4*17) = 4/204 и 3/208
5/36 и 7/54 = 5/(2*2*9) и 7/(2*3*9) = 15/108 и 14/108
9/35 и 11/42 = 9/(7*5) и 11/(7*6) = 54/210 и 55/210
4/49 и 5/63 = 4/(7*7) и 5/(7*9) = 36/441 и 35/441
15/98 и 13/72 = 15/(2*49) и 13/(2*36) = 540/3528 и 637/3528
5/12+11/24=10/24+11/24=21/24 и сокращаем на 3 получается 7/8
48x-17x=56
31x=56
x=56/31
x~1.8
Чёрных лошадей x+x(столько)+0.5x(полстолько)+1=100
2.5x+1=100
x=39.6