Hello,
Another way of looking at this is how much power does the resistor set draw from the power supply of 15v?
Since we know the source is 15v, if we know the current draw we can calculate the total power used by the resistors.
In the top picture, the total resistance is 15 ohms, and that means the top set draws 1 amp which means the source supplies 15 watts.
In the bottom picture, the total resistance is 15 ohms and that means the bottom set also draws 1 amp which means the source still supplies 15 watts.
Both circuits draw the same amount of current from a constant source voltage so they both dissipate the same power.
BTW, the short does nothing to change the circuit because it effectively jumpers two potentials that are EXACTLY the same for ALL time.
The only other way to look at this is from a statistical standpoint, where each resistor can be off by a certain tolerance like 10 percent. Given a random difference in each resistor, which set comes up statistically closer to 15 ohms total, or do they both come up the same anyway? See if you can figure this out
(Note that if each resistor can be off by a random amount up to 10 percent off, applying the short might then have an effect. If this were a real life circuit we might think about this too).