The Definition Of a Midpoint says that is B is the
midpoint of segment AC, then segment AB ≅ AC.
Since segment AB ≅ segment BC, we can setup
the equation 2(3x - 1) = 8x - 20 and we can solve from here.
Start by distributing the 3 through the parenthses on the left side.
So we get 6x - 2 = 8x - 20.
Now subtract 8x from both sides to get -2x - 2 = -20.
Now add 2 to both sides and we have -2x = -18.
Finally, dividing both sides by -2, we find that x = 9.
If x = 9, segment BC must be 3(9) - 1 or 27 - 1 which is 26.