We're given a set of exterior angles for a polygon, here a quadrilateral. Exterior angles of any polygon add to 360 degrees.
46 + (12x + 37) + (12x - 2) + (20x - 29) = 360
44 x + 52 = 360
44 x = 308
x = 308/44 = 7
Check: The supplementary angles should add to 360 as well, they're the interior angles of a quadrilateral
(180-46) + (180 - (12(7) + 37)) + (180 - (12(7) - 2)) + (180 - (20(7) - 29)) = 360, good
Answer: 7