Answer:
x = 4
Explanation:
The sum of two interior angles in a triangle is equal to an exterior angle that is supplementary to the third interior angles
46 + (-1 + 8x) = 18x + 5
46 - 1 + 8x = 18x + 5
45 + 8x = 18x + 5 export like terms to the same side
45 - 5 = 18x - 8x
40 = 10x divide both sides by 10
x = 4