RS is equal to 12.
In a circle, two chords that intersect inside of a circle is given by this formula: PR * RT = QR * RS
Since these two chords are equal, we can set up this equation by putting what we know so far. Since PR * RT = 15 * 14 = 60, and QR * RS = 5 * RS, we get 5 * RS = 60. This is just a simple algebraic expression now.
Dividing by 5 from both sides, we get
=
.
We then get RS = 12. This wasn't so bad, right?
Hope this helped!