The image is a bit hard to make out, so I'm going to make some guesses. It looks like it says \(PN=12\), \(QP=8\), and \(PM=17\), and you're asked to find \(QR\).
You know that \(\Delta NPM\) and \(\Delta NQR\) are similar, which means their corresponding sides are proportional in length. So there's some constant \(c\) such that
\(NP=cNQ\)
\(PM=cQR\)
\(MN=cRN\)
To find \(QR\), you need to know \(PM\) and the constant \(c\).
Clearly, \(NQ=NP+PQ=12+8=20\). So, the first equation becomes
\(NP=cNQ\iff12=20c\implies c=\dfrac{12}{20}=\dfrac35\)
Then in the second equation, you have
\(17=\dfrac35QR\implies QR=17\times\dfrac53=\dfrac{85}3=28.\overline3\)
