A circuit with two sources and three two port elements is studied. Some voltages and currents are given. Voltage of the voltage source is unknown. We need to analyze the circuit, find power of other elements and use the energy conservation to determine the power of the voltage source.
We go through solving a circuit which only containes independent sources: two voltage sources and two current sources. KVL and KCL are used to determine voltages and currents.
Superposition rule is used to solve a DC resistive circuit which has two independent voltage sources and four resistors.