Question 21

Let $QX=1$
$PX=6$
$XR=\frac{3}{2}$
$PM=\frac{PR}{2}=\frac{6+\frac{3}{2}}{2}=\frac{15}{4}=3\frac{3}{4}$
$MX=6-3\frac{3}{4}=2\frac{1}{4}=\frac{9}{4}$
$\frac{QX}{MX}=\frac{4}{9}$