please help - tough DS question

[genius_in_the_gene]

IMO A
1) x=y=50

2) Let ACD=a

now if we extend AD to E, then CDE= 140

now CDE= y+a
y+a=140
Since x=y
So we get x+a=140

a is still unknown.

[singalong]

IMO answer is A
AC is the traversal cutting the parallel lines BC and AD

1. Alternate angles y=x=50.Hence sufficient

2. z=40 but value of y is unknown.Even though we know the exterior angle theorem that angle= angle y+ angle z, we are still helpless as value of angle y is known to find value of angle x. hence insufficient.

So answer is A.