Answer:
x = 18
Explanation:
the sum of the 3 angles in a triangle is 180°
sum the angles, equate to 180 and solve for x
x - 6 + 5x + 6 + 3x + 18 = 180 ( collect like terms on left side )
9x + 18 = 180 ( subtract 18 from both sides )
9x = 162 ( divide both sides by 9 )
x = 18