Explanation:
Your teacher wants you to find the midpoint. This is the point that is in the middle of the two given points. Let's call this M. So the distance from M to (5,-5) will be the same as the distance from M to (1,1)
The x coordinates of (5,-5) and (1,1) are 5 and 1 respectively.
Add them up: 5+1 = 6
Divide by two: 6/2 = 3
The x coordinate of the midpoint is x = 3
Repeat for the y values -5 and 1
Add: -5+1 = -4
Divide in half: -4/2 = -2
The y coordinate of the midpoint is y = -2
So the midpoint is M = (x,y) = (3,-2)
If you were to use the distance formula, you would find that
distance from (5,-5) to (3,-2) = distance from (3,-2) to (1,1)
This is what it means to be "equidistant" (aka "equally distant")