Hello,
here is the picture:
Slope (PR):
[tex]m=\dfrac{2-4}{6-2} =-\dfrac{1}{2} \\Slope\ of\ the\ perpendicular: -\dfrac{1}{\dfrac{-1}{2} } =2\\\\perpendicular\ is\ passing\ trought\ M(4,3): y-3=2(x-4)\\y=2x-5\\If\ y=0\ then\ x= \dfrac{5}{2} \\Q=( \dfrac{5}{2},0)\\[/tex]