The lengths of the segments intercepted on the transversals are proportional. Let's write a proportion using the expressions for the lengths of the segments.
20-5x/2x+6=y/35y+2
Since we know that two segments on the left part of the diagram are congruent, we know that two segments on the right side are also congruent. Let's solve the equation y = 35y+2 to find y.