The values of a, b and c are 18°, 54° and 27° respectively
Angles on parallel lines are formed when a traversal cut through parallel line(s).
These angles can be alternate , opposite or corresponding to each other. In any of this case the angles are equal to each other.
7a + 3a = 180 ( adjascent angles on a straight line)
10a = 180
a = 180/10
a = 18°
b = 3a ( corresponding angles)
b = 3 × 18
b = 54°
b = 2c ( vertical angles)
c = 54/2
c = 27°
Therefore, the values of a, b and c are 18°, 54° and 27° respectively