Answer:
m<YAC = 64.5°
Step-by-step explanation:
m<BAC = 90°
m<BAC = m<BAY + m<YAC
m<BAC = (1/2)m(arc)BY + m<YAC
90° = (1/2)(51°) + m<YAC
m<YAC = 90° - 25.5°