notice that, if Q is the midpoint of PR, that simply means that PQ = QR = 43.
[tex]\bf \boxed{P}\underset{\leftarrow 9x-31 \to }{\stackrel{\stackrel{\downarrow }{43}}{\rule[0.35em]{10em}{0.25pt}}Q\stackrel{43}{\rule[0.35em]{10em}{0.25pt}}}\boxed{R} \\\\\\ 9x-31=43+43\implies 9x-31=86\implies 9x=117 \\\\\\ x=\cfrac{117}{9}\implies x=13[/tex]
