(y+15 7/8)-6 5/12=18 1/6

(y+15 7/8)-6 5/12=18 1/6
y+127/8-77/12=109/6
y+381/24-154/24-436/24=0
y-209/24=0
y=209/24
Ответ: y=209/24 или 8 17/24