You start by using the midpoint formula three times. First, find the midpoint of PQ. Let (x1, y1) be P(-2, 4) and let (x2, y2) be Q(-4, -4):
You have two points to find the equation of this median and R(6, 0). Find the slope, use point-slope form or slope-intercept form to find this equation. You'll see that the equation is y = 0.
Repeat the process to find the midpoint of QR. Let (x1, y1) be Q(-4, -4) and let (x2, y2) be R(6,0). Find the equation of the line between and P. Then do it one last time for PR, and find the equation of the line between and Q.