Answer:
x = 5
Step-by-step explanation:
The sum of the 3 angles in a triangle = 180°
Sum the 3 angles in the triangle and equate to 180, that is
10x - 4 + 8x + 3 + 91 = 180
18x + 90 = 180 ( subtract 90 from both sides )
18x = 90 ( divide both sides by 18 )
x = 5
