Answer: x = 4
==================================================
Step-by-step explanation:
Use the remote interior angle theorem. This says a pair of interior angles always add to the measure of the exterior angle that is not adjacent to any of the interior angles, so basically what your diagram is showing.
(interior angle C) + (interior angle D) = exterior angle
(46) + (-1+8x) = 18x+5
8x+45 = 18x+5
8x-18x = 5-45
-10x = -40
x = -40/(-10)
x = 4