Short Answer: n = 5
The chords bear the relationship of (in this case)
18*(n + 1) = 9 * (n +7) Remove the brackets
18n + 18 = 9n + 63 Subtract 9n from both sides.
18n - 9n + 18 = 63
9n + 18 = 63 Subtract 18 from both sides.
9n = 63 - 18
9n = 45 Divide by 9
n = 45/9
n = 5 <<<<<<<< Answer