The full length of one line times the length of the line outside the circle is equal the the other line.
(x-1) +5 x 5 = (2+x)+4 x 4
Simplify:
(x+4) x 5 = (x +6) x 4
5x +20 = 4x +24
Subtract 20 from each side:
5x = 4x +4
Subtract 4x from each side:
x = 4
The answer is B. 4