we know,
angle b= angle c
=>AB=AC(lines opposite to equal angles are equal)
=> 1/2x+5=5/6x+7
=>5/6x-1/2x= 5-7
=>2x/6= -2
=>x= -6
Now,
BC= 2/3x+7
=2/3×-6 +7
=-4 +7 = 3
therefore BC=3
I hope this is correct and helps you
