You know that the sum of angles of line CX has to be 180 degrees. Therefore, because you know angle EDX equals 134 degrees, and 180-134= 46, you know that angle CDE equals 46 degrees. Because you know the 3 interior angles of a triangle equals 180 degrees, if you subtract 180 - 46 - 105 = 2x-13. This simplified is 29= 2x-13. Further simplified, 42=2x. Therefore x=21 degrees.