In a bomb-calorimeter experiment, the can is filled with 2.0 kg of water. one gram of substance of known energy content 28.5 mj/kg is burnt and the observed temperature rise is 2.76 °c. determine the heat capacity of the metal parts of the calorimeter. the specific heat capacity of water over the temperature range is 4.187 kj/kgk

So we have 2kg of water increasing in temperature by 2.76 degrees. This gives us 4.187*2kg*2.76C = 23.1kJ of energy. 
1 gram of the fuel is given by 28.5MJ/kg * 0.001kg = 28.5kJ of energy.
Subtracting the energy the water took from the fuels total energy leaves the energy absorbed by the metal parts: 28.5-23.1 = 5.4kJ. 
Since this was raised by the same 2.76C we can say that the heat capacity is 1.95kJ/C. Notice the units, since we don't not know the mass of the can.