Question 389063
From the law of cosines,
{{{PQ^2=QR^2+PR^2-2(QR)(PR)cos(R)}}}
{{{cos(R)=(QR^2+PR^2-PQ^2)/(2(QR)(PR))}}}
{{{cos(R)=(20^2+23^2-25^2)/(2(20)(23))}}}
{{{cos(R)=304/920}}}
{{{cos(R)=0.3304}}}
{{{highlight(R=70.7)}}} degrees