1 mole of CH4 releases -434kJ of energy (the coefficient on CH4 would be 1, and therefore there is 1 mole of CH4 in that equation). Since we want to find out how much energy 1.2 moles would release, we have to use that information as a conversion factor. Start with 1.2 moles, multiply by .434kJ/1 mole.
When 1.2 moles of methane react the released energy is:
434 x 1.2 = 520 kJ = 5.2 x 10^5 J