Question

The δe of a system that releases 12.4 j of heat and does 4.2 j of work on the surroundings is __________ j.

Answer 1

The answer for this problem is clarified through this, the system is absorbing (+). And now see that it uses that the SURROUNDINGS are doing 84 KJ of work. Any time a system is overshadowing work done on it by the surroundings the sign will be +. So it's just 12.4 KJ + 4.2 = 16.6 KJ.