find the value of x and explain

Answer:
D
Step-by-step explanation:
The chord- chord angle 105° is half the sum of the arcs intercepted by the angle and its vertical angle, thus
[tex]\frac{1}{2}[/tex](120 + x) = 105 ( multiply both sides by 2 )
120 + x = 210 ( subtract 120 from both sides )
x = 90 → D