In the accompanying diagram, line a intersects line b.

Answer:
C. 10
Step-by-step explanation:
[tex] (x + 5) = (2x - 5) [/tex] (vertical angles are congruent)
[tex] x + 5 = 2x - 5 [/tex]
Add 5 to both sides
[tex] x + 5 + 5 = 2x [/tex]
[tex] x + 10 = 2x [/tex]
Subtract x from both sides
[tex] 10 = 2x - x [/tex]
[tex] 10 = x [/tex]
[tex] x = 10 [/tex]