(1) Angles of the quadrilateral are 90º, 90º, x, and y, where x + y = 180º.
Clearly, x and y can take any values so that they add to 180. So, we don't get a unique answer.
Hence, (1) is NOT SUFFICIENT.
(2)
x + 2x + a + d = 360º
Again, we don't get a unique answer.
Hence, (2) is NOT SUFFICIENT.
Combining (1) and (2), we don't know which two angles of ABCD are 90º.
It may be possible that 2x = 90 or x = 45, which implies angles of the quadrilateral are 90, 90, 45, and 135 (notice here that 90 = 2(45), which satisfies the 2nd condition.)
If a = d = 90, x = 60, and 2x = 120, then one of the interior angles is 60º.
From the above examples, it is clear, that one of the interior angles may or may not be 60º.
So, combining the two statements is also NOT SUFFICIENT.
The correct answer is E.