9514 1404 393
Answer:
C 21
Step-by-step explanation:
You can approach this any of several ways. The following conditions must be true:
adjacent angles total 180°
opposite angles are congruent
Using the latter relation on the upper right and lower left angles, we have ...
4x -1 = 3x +20
x = 21 . . . . . . . . . . add 1-3x to both sides
