we know B is the midpoint, thus it cuts AC into two equal halves.
[tex]\bf \underset{\textit{\Large 8x - 20}}{\boxed{A}\stackrel{3x-1}{\rule[0.35em]{10em}{0.25pt}} B\stackrel{3x-1}{\rule[0.35em]{10em}{0.25pt}}\boxed{C}} \\\\\\ (3x-1)+(3x-1) = 8x-20\implies 6x-2=8x-20\implies -2=2x-20 \\\\\\ 18=2x\implies \cfrac{18}{2}=x\implies \blacktriangleright 9=x \blacktriangleleft \\\\\\ BC=3x-1\implies BC=3(9)-1\implies \blacktriangleright BC=26 \blacktriangleleft[/tex]
