Answer:
a = 30 degrees; b = 60 degrees; and c = 105 degrees.
Explanation:
Angle a and the 30 degree angle are vertical angles and thus are equal.
Since the interior angles of a triangle always add up to 180 degrees, 30 + b + 90 degrees = 180 degrees, so that b must be 60 degrees.
Angle c and the 75 degree angle are straight angles, and so their sum must be 180 degrees. Thus, c = 105 degrees.