Question

A capacitor consists of a solid metal sphere of radius 3 cm placed at the center of a thin metal spherical shell of radius 12 cm. The space between is empty. What is the capacitance?

Answer 1

For the solution to this problem (and the formula to use for C), see
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capsph.html

You will need the value of epsilon-zero, which I presume you have learned.

Answer 2

Thank you so much for your help! I got the answer.