Final answer:
To find AC, substitute the given values into the equation AC = AB + BC.
Step-by-step explanation:
Given that AB = 6, AC = -1 + 14x, and BC = 7x, we can find AC by substituting the given values into the equation AC = AB + BC.
Substituting AB = 6 and BC = 7x, we have AC = 6 + 7x.
Therefore, AC = 6 + 7x.