The sum of the interior angles of the triangle is 180°. Interior angle A is congruent to the alternate interior (with respect to the parallel lines) angle marked 2x at E. The interior angles at B and E are the supplements of the exterior angles at those points.
500 = 200 + 20h is our equation. Subtract 200 from both sides 300 = 20h Divide by 20 300/20 = 15. It will take 15 hours to get 500 points. Hope this helps!