Gravity is proportional to 1/r^2 (r being distance), so you could take a stab at computing your ISS question with that info.
The centripetal force question is a little more challenging, but still in the realm of algebra. The complicated part is setting up the problem and understanding where the forces are coming from and if/how they cancel each other.
The centripetal force question is a little more challenging, but still in the realm of algebra. The complicated part is setting up the problem and understanding where the forces are coming from and if/how they cancel each other.