Since line AB and line BC are congruent, you equal them to each, which will give the 'x' to substitute into line AB
[tex]3x = 4x -2[/tex]
Subtract -4x from both sides of the equation.
[tex]-x=-2[/tex]
Then divide -1 from both sides of the equation.
[tex]x=2[/tex]
Then you do 3(2) which is 6.
The answer is B
