Answer :
[tex]\Delta QRN\sim\Delta PMN\\\\\frac{|QR|}{|QN|}=\frac{|PM|}{|PN|}\\\\\\\frac{|QR|}{8+12}=\frac{17}{12}\\\\\frac{|QR|}{20}=\frac{17}{12}\ \ \ /\cdot20\\\\|QR|=\frac{17}{12}\cdot20\\\\|QR|=\frac{17}{3}\cdot5\\\\|QR|=\frac{85}{3}\\\\|QR|=28\frac{1}{3}[/tex]
