WAEC Mathematics 2025 Paper

Concept:Angles on a straight line add up to $180^\circ$, and the interior angles of a quadrilateral add up to $360^\circ$.Explanation:Identify the quadrilateral formed inside the diagram.Let $\angle BFC$ be the angle at the point where the straight lines meet.Since angle $a$ and $\angle BFC$ lie on the same straight line,$\angle BFC = 180^\circ - a$.The four interior angles of the quadrilateral sum to $360^\circ$:$a + b + c + \angle BFC = 360^\circ$.Substitute the value of $\angle BFC$:$a + b + c + (180^\circ - a) = 360^\circ$.Simplify:$b + c + 180^\circ = 360^\circ$.Therefore,$b + c = 180^\circ$.Answer:$b + c = 180^\circ$, so the correct option is C. $180^\circ$.