Chemistry (Enthalpy) Problem

 Spoiler

This problem's making me mad, because I'm doing exactly as someone else says and getting the wrong answer, supposedly. Got three heat equations, get delta H for the combustion of methane, then divide delta H by Qtotal, and multiplied by the molar mass of methane. Which is wrong.

Haven't slept and about to have to leave for work. Sorry I couldn't go into more detail about what I did, but if someone could help me I'd really appreciate it.