Online Geometry Problem 855: Quadrilateral, Triangle, Angles, 30 degrees,
Congruence, Auxiliary lines. Level: High School,
SAT Prep, College,
Mathematics Education

The figure below shows a quadrilateral ABCD
with angle BAC = angle CAD = 13 degrees, angle ACB = 30 degrees, and
angle CBD = 86 degrees. Find the measure of angle ACD. Try to use elementary geometry (no
trigonometry).