Final answer:
The change in internal energy (ΔE) of the system is calculated using the first law of thermodynamics. With 1275 J of heat added to the system and 855 J of work done by the system, ΔE equals 420 J.
Step-by-step explanation:
To calculate the change in internal energy (ΔE) of a system in joules, we can use the first law of thermodynamics, which is ΔE = Q - W, where Q is the heat added to the system and W is the work done by the system on its surroundings. In this case, the system receives 1275 J of heat (Q) and performs 855 J of work (W) on the surroundings.
Using the equation, the change in internal energy is:
ΔE = Q - W
ΔE = 1275 J - 855 J
ΔE = 420 J
Thus, the change in internal energy of the system is 420 J.