Answer:
7
Step-by-step explanation:
The external angle of a triangle is equal to the sum of the opposite interior angles
18x+9 = 5x-5 + 105
Combine like terms
18x+9 = 5x +100
Subtract 5x from each side
18x-5x +9 = 5x+100-5x
13x +9 = 100
Subtract 9 from each side
13x +9-9=100-9
13x= 91
Divide by 13
13x/13 = 91/13
x = 7
