In triangle ABC, m∠ABC = (4x - 12) ° and m∠ACB = (2x + 26) °. Yin says that if x = 19, the triangle must be equilateral. Is he correct? Justify your answer

If x = 19 m∠ABC = (4.19 - 12) °=64°, and m∠ACB = (2.19 + 26) °=64°

so the other angle can be found with

m∠ABC + m∠ACB + m∠CAB = 180°

m∠CAB = 180°-m∠ABC - m∠ACB = 180°-128°=52°

so the triangle is not aquilateral,

he was wrong