Angles a and b are vertical, so they are congruent.
The left triangle has 3 angles: 90 deg, 65 deg, and a.
We can find the measure of angle a.
a + 90 + 65 = 180
a = 25
Since a and b are vertical, and b is congruent to a,
b = a = 25 deg
Answer: D. 25 deg