Since B is the midpoint of AC, the segments AB and BC must have equal length. This means that x + 13 = 2x + 3. Solving this, we see that x = 10. By substituting 10 for x, we see that the length of AB is 23, so the length of AC is 2*23, which is 46.
The answer is going to be 2*sqrt(5). You have to split it into perfect squares for it to be simplified... so in this case, I had sqrt(4*5) because sqrt(4) can be simplified... so your answer would be sqrt(4)*sqrt(5) or 2sqrt(5)
