More algebra pretending to be geometry. These questions should be banished from the planet.
A transversal across parallel lines generates the usual congruent and supplementary angles; here our pair are supplementary, adding to 180 degrees. Geometry done.
(2x + 12.8) + 117.6 = 180
2x = 180 - (12.8 + 117.6) = 49.6
x = 49.6/2 = 24.8
Answer: 24.8