You need to work out the other angles first, before working out the values of; a, b and c.
∠x = 180 - 139 [∠'s on a straight line]
thus, ∠x = 41°
∠y = ∠x [corresponding angles]
∴ ∠y = 41°
∠h = 180 - (41 + 77 + 36) [∠'s on a straight line add to 180°]
∠h = 26°
∠p = ∠h + 77° +∠y [corresponding ∠'s]
∴ ∠p = 26 + 77 + 41
∠p = 144°
∠a = 180 - (26 + 77 + 41) [∠'s on a straight line]
∠a = 180 - 144
thus, ∠a = 36°
∠c = 36 + ∠h [corresponding ∠'s]
∠c = 36 + 26
∴ ∠c = 62°
∠b = 180 - ∠c [∠'s in a straight line add to 180°]
∠b = 180 - 62
thus, ∠b = 118°
Hope you followed through. :)
