Question 704146
The medians connect one vertex to the midpoint of the other side
 
RA is a median, so A must be the midpoint of ST, and
the coordinates of A are the averages of the coordinates of S and T:
{{{x[A]=(-5-2)/2=-7/2=-3.5}}} and {{{y[A]=(5-2)/2=3/2=1.5}}}.
 
Similarly, the coordinates of B are
{{{x[B]=(-9-2)/2=-11/2=-5.5}}} and {{{y[B]=(-3-2)/2=-5/2=-2.5}}}.
 
And the coordinates of C are
{{{x[B]=(-9-5)/2=-14/2=-7}}} and {{{y[B]=(-3+5)/2=1/2=1}}}.
 
I think you were expected to graph the whole thing,and get something like this:
{{{drawing(300,300,-11,1,-5,7,
grid(1),
red(circle(-9,-3,0.2)),red(circle(-5,5,0.2)),red(circle(-2,-2,0.2)),
red(triangle(-9,-3,-5,5,-2,-2)),
blue(circle(-7,1,0.2)),blue(circle(-3.5,1.5,0.2)),blue(circle(-5.5,-2.5,0.2)),
green(line(-7,1,-2,-2)),green(line(-3.5,1.5,-9,-3)),green(line(-5.5,-2.5,-5,5))
)}}}
 
When you split a triangle in two with a median,
the two pieces are triangles with the same area.
They have bases (the split side) of the same length,
and the height from that base to their shared vertex is the same.
The medians meet at the "center of gravity" of the triangle.
 
If you draw a triangle, cut it out, and draw the medians,
you can stick a pin anywhere in the triangle,
let it dangle freely (maybe the pin hole needs to get a little larger),
and the point where the medians cross should hang directly below the pin.
 
That point has a fancy name, you can look it up.
Is it incenter, circumcenter, centroid, orthocenter, or something else?