geometry
posted by ari .
The following are angles in a convex quadrilateral:
Angle A = 75.3 degrees
Angle B = 114.8 degree
Angle C = 65.9 degrees
What is the measure of the missing angle?

Add the three angles together and subtract from 360.
http://www.geom.uiuc.edu/~dwiggins/conj06.html