The topic of this problem is Series and Parallel Independent Sources, and

the problem is to determine the current in the circuit that’s drawn and

the power associated with the 5 ohm resistor.

In this problem, we have a series combination of Voltage sources and

resistors.

And we know that we can combine series voltage

sources by adding them, and so that's what we're going to do in this problem.

We first of all acknowledge that the 5V sources, all three of them,

are a series of one another.

And we combine those, and we get a 15 volt source as shown in the redrawn circuit.

And the way that we get that is by going clockwise around the circuit with

the negative polarity and the 5 volt source on the right hand side first.

That's minus 5 volts.

We could continue in the top part of the circuit.

We hit the negative polarity of the 5 volt source at the top.

So it's a minus 10 volts combining those two.

And continually around the circuit in clockwise fashion,

we hit the negative polarity of the 5V source on the right hand side.

So that's how we ended up with a 15V source on the left hand side of our

redrawn circuit.