Answer is #2. = 21
Step by step
We can see angle 5x is a vertical angle to a 90 degree angle and 15 degree angle combined.
So we know vertical angles are congruent (the same) so we can use the equation
90 + 15 = 5x
Solve for x
105 = 5x
Divide both sides by 5 to solve for x.
21 = x
Problem solved
