1) We can see here a case in which there are two secant lines coming from a single point over that circle.
2) So, we can write out the following relation
[tex]\begin{gathered} PA\cdot PB=PC\cdot PD \\ 4(4+x)=5(5+7) \\ 16+4x=25+35 \\ 16+4x=60 \\ 16-16+4x=60-16 \\ 4x=44 \\ \frac{4x}{4}=\frac{44}{4} \\ x=11 \end{gathered}[/tex]
