First we substitute у=1,4/11 into the expression:

1/14(1,4/11) + 8/21(1,4/11) - 3/35(1,4/11)

Next, we simplify the expression:

1/14(14/11) + 8/21(14/11) - 3/35(14/11)
= 1/11 + 16/11 - 6/11
= (1 + 16 - 6)/11
= 11/11
= 1

Therefore, when у=1,4/11, the expression simplifies to 1.