The product of external length and total length is the same for each secant. That is
EC×ED = EB×EA
(x+4)(x+4+1) = (x+1)(x+1+11) . . . . . . substitute values from the diagram
x² + 9x + 20 = x² + 13x + 12 . . . . . simplify
8 = 4x . . . . . . . . . . . . . . . . . . . . . . . subtract x²+9x+12
2 = x . . . . . . . . . . . . . . . . . . . . . . . . divide by 4
The value of x is ...
x = 2
