Question 252712
We have the coordinates
A (-3,3) and B(1,-8) 
to find midpoint, we need the following formula:
{{{(X1 + X2)/2}}} , {{{(Y1 + Y2)/2}}}
putting in our numbers, we get
(-3 + 1)/2 , (3 + -8)/2 - -> (-1, -5/2)
To find length, we need distance formula, which is
{{{d = sqrt((x1-x2)^2 + (y1 -y2)^2)}}}
again putting your numbers in, we get
{{{d = sqrt((-3-1)^2 + (3-(-8))^2)}}}
{{{d = sqrt((-4)^2 + (11)^2)}}}
{{{d = sqrt(137)}}}
d ~ 11.70 ~ 11.7