Hess's Law Chemistry Question?

I got -177.9 KJ ... flip the second reaction (changing the enthalpy to possitive). Multiply the first equation by 2 to get 1 mol of O2 on both sides (dont forget to multiply the enthalpy by 2). Then add the two enthalpy's together. Then divide the answer by 2 in order to get the reaction that you were trying to calculate.