Angles ODC and OBC= 90*
Because the angle between a tangent and a radius is a right angle.
Angle COD = Angle DFB x 2
= 76 x 2
= 152*
Because the angle at the center of the circle is twice the size of the angle on the circumference.
OBCD is a quadrilateral
The sum of angles of a quadrilateral = 360*
Angle BCD = 360 - (152 + 90 + 90)
= 28*