Question 1068635
The midpoint is the average of the coordinates,
{{{x[m]=(4+9)/2=13/2}}}
{{{y[m]=(20+23)/2=43/2}}}
Use the distance formula,
{{{D^2=(4-9)^2+(20-23)^2=(-5)^2+(-3)^2=25+9=34}}}
{{{D=sqrt(34)}}}