JAMB 1983 · UME · Q35

One interior angle of a convex hexagon is $170^\circ$ and each of the remaining interior angles is $x^\circ$ . Find $x$ .

Worked solution (try it first)

The interior angles of a hexagon add up to $(6 - 2) \times 180^\circ = 720^\circ$ .
One angle is $170^\circ$ and the other five are $x$ each, so $170 + 5x = 720$ .
Subtract 170: $5x = 550$ .
Divide by 5: $x = 110$ , option B.