JAMB 1985 · UME · Q49

The interior angles of a quadrilateral add up to $360^\circ$.

The three marked angles add up to $20^\circ + 80^\circ + 40^\circ = 140^\circ$.

So the interior angle at the inward-pointing vertex is $360^\circ - 140^\circ = 220^\circ$, a reflex angle.

$x$ is the angle on the other side of that vertex, and angles at a point add up to $360^\circ$: $x = 360^\circ - 220^\circ = 140^\circ$, option E.