I have to find the specific heat capacity of a rock that is 1910J/Kg Cdegrees. It has rock mass of 0.275kg. Falls from rest from a height of 28.5m and into a containing 0.480kg water. The rock and water has the same initial temp.

I'm using this equation:
T= Mrock(gh)
CrockMrock + CwaterMwater

I'm getting an answer of 0.030 Cdegrees but my computer assignment is saying this is the wrong answer. Please help me.

Your second equation is missing something. Besides, it is not clear how you used these two equations together. Or is this one equation? Remember also: what you have calculated using potential energy of the stone and heat balance is the temperature increment, not the temperature itself.