Answer:
x = 84
Explanation:
the sum of the interior angles of a polygon is
sum = 180° (n - 2) ← n is the number of sides
a pentagon has 5 sides , so n = 5
sum = 180° × (5 - 2) = 180° × 3 = 540°
sum the interior angles and equate to 540
x + x + 20 + x + 20 + x + 40 + x + 40 = 540
5x + 120 = 540 ( subtract 120 from both sides )
5x = 420 ( divide both sides by 5 )
x = 84