Circle (3)

<BCA = x

Use the same reasoning as problem 2.

<BAC = x (property of isosceles triangle)

So <ABC = 180 - x - x = 180 - 2x (property of triangle)

<ADC = 102

<ADC + < ABC = 180 (a cyclic Quadrilateral's opposite angles add to 180°)

102 + (180 - 2x) = 180
x = 51