This problem, when you read it, may seem scaring, I mean difficult to solve. You soon thnkg how to relate the mass of CH4 and it combutions with the change in temperature of thw water and the calorimeter.
But when you read it carfully (twice) you realize tha the question is the change in temperature and you are given both the initial and the final temperatures, then you just must subtract the initial temperature from the final temperature to get the answer:
ΔT = Final temperature - Initial temperature = 35,65°C - 24,85°C = 10.80 °C.
Answer: 10.80°C.
