Answer:
80 degrees, explanation down below
Step-by-step explanation:
according to the vertical angle theorem, two vertical angles are the same angle measure. so, angle CBD and angle ABF must be the same. this is 100 degrees. now, according to the corresponding angles theorem, corresponding angles are supplementary to each other (they add up to 180 degrees), so angle ABF and angle EFB are supplementary. since angle ABF is 100 degrees, we can subtract that from 180 degrees. therefore, angle x (same thing as EFB) is 80 degrees.
