Answer:
x = 10
Explanation:
the chord- chord angle 60° is half the sum of the measures of the arcs intercepted by the angle and its vertical angle , that is
(6x + 13 + 4x + 7) = 60
(10x + 20) = 60 ← multiply both sides by 2 to clear the fraction
10x + 20 = 120 ( subtract 20 from both sides )
10x = 100 ( divide both sides by 10 )
x = 10