find the unknown angle
how to solve this problem??

a)Find x and y
BCD=ACB+ACD
180°=ACB+150°
ACB=180°-150°
ACB=30°
since triangle ABC is an isosceles triangle
therefore, AB=BC
BAC=ACB
y=ACB=30°
ACB+ABC+BAC=180°
ABC+2BAC=180°
ABC+2*30°=180°
ABC=180°-60°
ABC=120°
X=120°