Answer:
sum of exterior angles of a polygon = 360°
therefore,
x + 5 + x + 10 + 3x - 8 + 5x + 10 = 360°
10x + 17 = 360°
x + 17 = 360 ÷ 10 = 36
x = 36 - 17 = 19
x = 19
value of x will be 20