Answer:
AC = 6.7
Explanation:
If this is a 90 degree triangle which I am assuming it is you would the Pythagorean theorem c^2 = a^2 + b^2 since bc seems long I am using that as the hypotenuse.
9^2 = 6^2 + b^2
81 = 36 + b^2
81-36 = b^2
45 = b^2
6.7 = b
so AC = 6.7