Mmm, tricky question.
Base knowledge needed: the sum of the interior angles of a quadrilateral is 360.
(1) gives us w = 95, which makes the lower-left interior angle 85. Thus, the three remaining angles sum to 275. Not enough information here, since we don't know anything about the lower-right interior angle. Insufficient.
(2) gives us z = 125, which makes the lower-right interior angle 55. The three remaining angles sum to 305. Not enough info, and now we don't know anything about the lower-left interior angle. Insufficient.
Together, however, we see that the remaining two angles must sum to 360 - 85 - 55 = 220. So, (180 - x) + (180 - y) = 220. You can see that this equation can be solved for x + y, and so together, (1) and (2) are sufficient. C.
(If you were curious, x + y = 140)
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