The coordinates of points m, n, and p are

(-1, -1) Let me know if the explanation didn't make sense.  

Step-by-step explanation:

If we graph the three points we can see what looks like a quadrilateral's upper right portion, so we need a point in the lower left.  This means M is only connected to N here and P is only connected to N.  So we want to find the slope of these two lines.

MN is easy since their y values are the same, the slope is 0.

NP we just use the slope formula so (y2-y1)/(x2-x1) = (-1-3)/(5-4) = -4.

So now we want a line from point M with a slope of -4 to intersect with a line from point P with a slope of 0.  To find these lines  weuse point slope form  for those two points.  The formula for point slope form is y - y1 = m(x-x1)

y-3 = -4(x+2) -> y = -4x-5

y+1 = 0(x-5) -> y = -1

So now we want these two to intersect.  We just set them equal to each other.

-1 = -4x -5 -> -1 = x

So this gives us our x value.  Now we can plug that into either function to find the y value.  This is super easy of we use y = -1 because all y values in this are -1, so the point Q is (-1, -1)