The Intersecting Chords theorem states that the products of the line segments on each chord are equal. In other words,
![UM\cdot UN=UJ\cdot UK](https://img.qammunity.org/2023/formulas/mathematics/high-school/badk8lly03a6l4q790xo9keslgab9mrctv.png)
We already know that UM = 26, UJ = 13, and UK = 39. Putting these values in the above equation gives us
![26\cdot UN=13\cdot39](https://img.qammunity.org/2023/formulas/mathematics/high-school/ievysermfnezxet55iofbfscygy149gg2j.png)
![26\cdot UN=507](https://img.qammunity.org/2023/formulas/mathematics/high-school/v8b180pl23ujarm7m2s71xyrdz73mazr65.png)
Dividing both sides by 26 gives
![\textcolor{#FF7968}{UN=19.5.}](https://img.qammunity.org/2023/formulas/mathematics/high-school/xb3q1z0308lhkow23l5ty5yz2be51sxrwh.png)
which is our answer!