Question

A closed system’s internal energy changes by 178 J as a result of being heated with 658 J of energy.
The energy used to do work by the system is ____________ J.

Answer 1

Internal energy of the system changes by ΔE = 178 J.
Heat given to the system = Q = +658 J.

According to the first law of thermodynamics, 
ΔE = Q + W
178 = 658 + W 
∴ W = 178-658 = -480 J

Minus sign indicates that work is done by the system.