How did the internal energy of the gas change, if, when the gas was supplied with 600J of heat, it did 400J of work?

Let’s find out how the internal energy of the gas has changed according to the following formula:

DU = Q – A, where DU is the change in internal energy in an equilibrium process, Q is the amount of heat received by the system in the process under consideration, A is the work that the system has performed.

DU = 600 J – 400 J = 200 J.

Answer: 200 J.