This chemistry problem is a combination of different skills I am supposed to have picked up on. Help?

Question

A 10.0-g sample of a mixture of CH4 and C2H4 reacts with oxygen at 25.0 degrees C and 1.00 atm to produce CO2(g) and H2O(l). If the reaction produces 519 kJ of heat, what is the mass percentage of CH4 in the mixture?

Answer 1

My reference says the Heat of combustion data for:
Methane: 50.009 kJ/g
Ethane: 47.794 kJ/g
Suppose we have X grams of CH4 in the mixture:
50.009 X + 47.794 (10.0 - X) = 519kJ
Obviously my referenced Heat of combustion data does not yield a solution for this problem.

But if you have a different set of data of Heat of combustion, you may get a correct solution just by following my method.