15 3/28 - (4 11/28 + y) = 7-1 9/28
15 3/28 - (4 11/28 + y) = 5 19/28
4 11/28 + y = 15 3/28 - 5 19/28
4 11/28 + y = 9 12/28
y = 9 12/28 - 4 11/28
y = 5 1/28
15 3/28 - (4 11/28 + y) = 7-1 9/28
15 3/28 - (4 11/28 + y) = 5 19/28
4 11/28 + y = 15 3/28 - 5 19/28
4 11/28 + y = 9 12/28
y = 9 12/28 - 4 11/28
y = 5 1/28