in the xy-plane, the z-component is 0. so use the distance formula to find the distance between (3,7,-5) and (3,7,0)

similarly, for the xz-plane, find the distance between (3,7,-5) and (3,0,-5)

and for the yz-plane, find the distance between (3,7,-5) and (0,7,-5)

this site looks neat. draw your diagram, fill in the required measurements, enter then in the required fields and follow the solution given.

plug in the points, you will get:

$\displaystyle \left< x - a_1, y - a_2, z - a_3 \right> \cdot \left<x - b_1, y - b_2, z - b_3 \right> = 0$

take the dot product and simplify to get the form: $\displaystyle (x - h)^2 + (y - k)^2 + (z - m)^2 = R^2$

the center is (h,k,m) and the radius is R