**Calculate the unknown marked angles in each figure :**

###### Answers:

We know that, the sum of three angles of a triangle is 180°, therefore

(i) In figure (i),

90° + 30° + x = 180°

⇒ 120° + x = 180°

⇒ x = 180° – 120° = 60°

Hence, x = 60°

(ii) In figure (ii),

y + 80° + 20° = 180°

⇒ y + 100° = 180°

⇒ y = 180° – 100° = 80°

Hence, y = 80°

(iii) In figure (iii)

a + 90° + 40° = 180°

⇒ a + 130° = 180°

⇒ a = 180° – 130° = 50°

Hence, a = 50°