Question

Three angles of a quadrilateral measure 56°, 115° and 84°. Find the measure of the fourth angle.

Answer 1

Let the measure of the fourth angle be x^o.
Since the sum of the angles of a quadrilateral is 360^o, we have:
56 + 115 + 84 + x = 360
⇒ 255 + x = 360 ​
⇒ x = 105
Hence, the measure of the fourth angle is 105^o.