we have give the two circles and chords QR is congruent to LN.
it means QR=LN
-x=y+8
and OP is congruent to VW
OP=VW
x=3y+8
we know that -x=y+8
+x=-y-8
we need to equate two equations
we know that chords subtends in two congruent circles are same .
-y-8=3y+8
4y=16
y=4.