Answer:
12sqrt(3)
Explanation:
The diagram is below.
Since triangle ABC is a 30-60-90 triangle, we have BC = AB/2 = 6, and AC = BCsqrt(3) = 6sqrt(3).
Since angle ABC equals 60 degrees and BX bisects angle ABC, we have angle CBX equal 30 degrees, so BXC is a 30-60-90 triangle.
Since CX is opposit the 30 degree angle in triangle BXC, we have:
CX = BC / sqrt(3) = 6 / sqrt(3) = 2 sqrt(3).
Therefore, AX = AC - CX = 4 sqrt(3).