Posted by HELP PLS MARVELOUS on Wednesday, January 9, 2013 at 8:04am.
ABCD is an inscribed quadrilateral. AD, BC are produced to meet at X. If angle B= 80 degrees and angle X= 30 degrees, find angle XCD.

GEOMETRY  Reiny, Wednesday, January 9, 2013 at 8:47am
I will assume you mean "inscribed in a circle"
In a cyclic quadrilateral, the opposite angles are supplementary, so angle D = 100°
Also angle ADC is an exterior angle in triangle DCX, so
angle DCX + angle CXD = angle ADC
angle DCX + 30 = 100
angle DCX = 70° 
GEOMETRY  Anonymous, Friday, January 11, 2013 at 1:39am
30

GEOMETRY  Jovan Alvin Tapalla, Monday, January 13, 2014 at 2:22am
50 degrees