the tickmarks on the vertices of B and C mean that those angles are twins, which means that the sides AB = AC, which means is an isosceles triangle.
now if AB = AC, then
[tex]\bf 8x-4=5x+11\implies 3x=15\implies x=\cfrac{15}{3}\implies \boxed{x=5} \\\\\\ BC\implies 4x-2\implies 4(5)-2\implies 18[/tex]
