Ineed on this how do you find the third measure

The sum of the three angles of a triangle is always 180°. Tha is
  (first measure) + (second measure) + (third measure) = 180°

Subtract the first two terms of this equation and you have
  (third measure) = 180° - (first measure) - (second measure)

a. third measure = 180° - 45° - 55° = 80°

b. third measure = 180° - 50° - 40° = 90°

c. third measure = 180° - 110° - 35° = 35°