Answer:
x = 27
Explanation:
The sum of the interior angles of a polygon is
sum = 180° (n - 2) ← n is number of sides
Here n = 7 , then
sum = 180° × 5 = 900°
sum the interior angles and equate to 900
3x + 31 + 135 + 5x - 4 + 7x - 64 + 120 + 6x - 8 + 4x + 15 = 900 , that is
25x + 225 = 900 ( subtract 225 from both sides )
25x = 675 ( divide both sides by 25 )
x = 27