A. 54
The fact that B is the midpoint means that AB = BC so you can set up the equation of
4x+3 = 3x+9
Then solve for x by subtracting 3 from the left and 3x from the right to get
X=6
Finally, plug that back in to your line and solve for the total value
4(6) + 3 + 3(6) +9 = 54
