Answer:
72
Step-by-step explanation:
112 + 90 + 78 = 288
360 - 288 = 72
∠ = 80°
The sum of the interior angles of a quadrilateral = 360°
Subtract the sum of the 3 given angles from 360 for ∠C
∠C = 360° - (90 + 112 + 78 )° = 360° - 280° = 80°
