Step-by-step explanation:
AB = AC, so mark the two sides with single tick marks.
m∠ACD = 128°, so label the angle 128°.
∠ACB is supplementary to ∠ACD, so:
m∠ACB + m∠ACD = 180°
m∠ACB + 128° = 180°
m∠ACB = 52°
ΔABC is an isosceles triangle, so m∠B = m∠ACB.
m∠B = m∠ACB
m∠B = 52°
Angles of a triangle add up to 180°, so:
m∠A + m∠B + m∠ACB = 180°
m∠A + 52° + 52° = 180°
m∠A = 76°
