Since this triangle is an isosceles triangle , it's opposite base angles will be equal . Which means :-
∠a = ∠b ( opposite base angles )
Angle sum property :- Sum of all angles in the interior of a triangle will be equal to 180° .
Which means :-
80° + ∠a + ∠b = 180°
Let us name both the angles as 'n' as their values are equal . Then :-
80° + n + n = 180°
80° + 2n = 180°
2n = 180 - 80
2n = 100
n = 100 ÷ 2
n = 50
Which means :-
∠a = 50°
∠b = 50°
Value of ∠x :-
as x is the exterior angle it will be equal to the sum of its interior opposite angles .
∠x = 80° + 50°
∠x = 130°
Therefore , the value of ∠a = 50° and ∠b = 50° .
