Hi boomgoesthegmat,
This question requires an understanding of similar triangles, "line" rules (specifically that the angles on a line sum to 180 degrees) and that the angles in a triangle sum to 180 degrees.
We're told that Z=50. Since the two triangles have the same angles (they both have a 90 and the same angle "next" to angle X), we know that the triangles are similar. This means that Z and the angle "next" to Y are the SAME (meaning that they BOTH = 50).
By extension, Y + 50 = 180, so Y = 130.
The angles in the smaller triangle are 90, 50 and the missing angle. 90+50 = 140, so the missing angle = 40.
40 + X = 180, so X = 140
Thus, X+Y = 130+140 = 270
Final Answer: D
GMAT assassins aren't born, they're made,
Rich
