The square on the hypotenuse is skew and impossible to visually validate. There's nothing to sum. It is a simple calculation to note that <span><span><span>32</span>+<span>42</span>=<span>52</span></span><span><span>32</span>+<span>42</span>=<span>52</span></span></span><span>, but its picture doesn't 'say' that the angle between the 3 and 4 sided square must be 90 degrees.
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If the 3 points are collinear, then the slopes of all line segments connecting the points are the same.
Thus,
-6 - (-8) 2
m = ------------- = -------- = -1/2
-7 - (-3) -4
Then the following must be true:
4-(-6) 10
-1/2 = ------------ = ---------
c - (-7) c + 7
Cross multiplying, -(c+7) = 20, and c+7 = -20, so that c = -27
See the attached picture:
"Alia gets 4^2 fewer than Kelly, who gets 3^3."
So it's about a subtraction.

Hope this helps.
r3t40