In a quadrilateral ABCD,LA=150 and LB=LC=LD,f finLB,LC, AND LD

since its a quarilateral sum of all the angle = 360

<A= 150
<B=<C=<D=X

<A+<B+<C+<D=360
150+X+X+X=360
3X=360-150
3X=210
X=70

So,
<A=<B=<C=70