Answer:
x = 9
Step-by-step explanation:
Vertical angles are congruent ( equal to each other )
So if ∠A and ∠B are vertical angles than they are congruent ( so ∠A = ∠B )
If ∠A = 2x + 1 and ∠B = x + 10
Then 2x + 1 must equal x + 10
( note that we've just created an equation that we can use to solve for x )
We now solve for x using the equation we just created
2x + 1 = x + 10
Subtract x from both sides
x + 1 = 10
subtract 1 from both sides
x = 9
