7.) the equation of the circle is
(x - 3)^2 + (y - 4)^2 = 25
If you substitute the point in you get
(6-3)^2 + (8-4)^2 = 25
3^2 + 4^2 = 25
9 + 16 = 25
25 = 25
Both sides of the equation are the same so it proves it lies on the circle
8.) you add the x coordinates together and divide by 2
7 + 4 = 11
11/2 = 5.5
You use +7 because you need to find the midpoint.
You then add 5.5 to - 7 or - 5.5 from 4
-7 + 5.5 = - 1.5
You do the same for y coordinates
6+5 = 11
11/2 = 5.5
6-5.5 = 0.5
So the coordinates of Rachel's house are
(-1.5, 0.5)