Δ ABC is a right triangle:
To find angle C , you have to use trigonometry and precisely the tangent:
tan = side opposed to angle C/ side adjacent to C
tan c = 5/14 =0.357142. To find C, you should apply the inverse function in short tan⁻¹C (or arctan C),
Answer (use your calculator ):tan⁻¹(0.35714) =19°65 or 20°