Internal energy of the gas in a gasoline engine

[fletcher89]

I am so lost with this question. Can anyone help?

The internal energy of the gas in a gasoline
engine's cylinder decreases by 176:7 J.
If 67.0 J of work is done by the gas, how
much energy is transferred as heat? Answer
in units of J

 

[Harmony]

Use the first law of thermodynamic:
Q=U+W, where W is the work done by the gas

 

[fletcher89]

I did Q= 176.7 (change in energy) + 67 (amount of work done)

I got 243.7
What am I doing wrong

 

[i.mehrzad]

I think the mistake is here.
Q=U+W but since the work is fone by the gas the the +w might be deceiving.
W is positive if work is done on the gas.Since instead it is done by the gas it would imply you will have to add -67
Therefore the answer is 176.7-67=109.7