In a triangle ABC, if $$\angle A$$ + $$\angle C$$ = 140° and $$\angle A$$ +  3 $$\angle B$$ = 180° then $$\angle A$$ is equal to

Given : $$\angle A$$ + $$\angle C$$ = 140° ----------(i)

and $$\angle A$$ +  3 $$\angle B$$ = 180° ------------(ii)

To find : $$\angle A$$ = ?

Solution : In $$\triangle$$ ABC,

=> $$\angle A$$ + $$\angle B$$ + $$\angle C$$ = $$180^\circ$$

Using equation (i), => $$\angle B+140^\circ =180^\circ$$

=> $$\angle B = 180^\circ - 140^\circ = 40^\circ$$

Substituting it in equation (ii), we get :

=> $$\angle A + (3 \times 40^\circ)=180^\circ$$

=> $$\angle A=180^\circ-120^\circ$$

=> $$\angle A=60^\circ$$

=> Ans - (C)