KDL86 4/15 + y/15 = 1
(4+y)/15=1
y=11

8/15 - y/15 = 0
(8-y)/15=0
y=8

19/15 - y/15 = 1
(19-y)/15=1
y=4

1 - y/15=11/15
y/15+11/15=1
(y+11)/15=1
y=4