Question

In ∆ABC side BC is extended to point D, such that the exterior angle ∠ACD = 105°. If the interior opposite angles are in the ratio 3:4, find all angles of ∆ABC.​

Answer 1

exterior angle = sum of two interior opposite angles

so,

$3x + 4x = 105 \\ x = 15 \\ a = 3 \times 15 = 45 \\ b = 4 \times 15 = 60$