What is the change in internal energy in joules for a system that releases 154 j of heat and does 125 j of work on its surroundings?

The change in internal energy of the system is given by the first law of thermodynamics:

where 
Q is the heat added to the system
W is the work done by the system

In this problem,  (with a negative sign because the heat is released by the system (not absorbed)), and the work is , with a positive sign since it is performed by the system. Therefore, the variation of internal energy of the system is


So, the internal energy of the system has decreased.

The answer is b hope this