Calculating Resistance Between Points A and B in Circuit with -5V Across Resistor

After calculating the voltage across the resistor on the far right, I got it to be V=5Then I did a loop to get the resistance between A and B and I'm getting it to be zero because of that -5V. Is that correct,
https://drive.google.com/file/d/1VZR65QXl3OSM4sflsg1wv2UG_D9Ikp_d/view?usp=drivesdk

Hi Kabelo. Look at it this way.  The 20V battery and the associated 150 ohm resistor are across the 10V battery.  Now batteries in this mythical land of circuit analysis always have zero internal resistance and infinite capacity, so the 10V will stay at 10V.  So the 20V and 150 ohm are just a distraction.So the other two 150 ohm resistors are dividing the 10V supply in two, so there will be +5V at the negative end of the of the 5V battery, as you found.    But the 5V battery will add to this and you'll have 10V across A and B, with no load on A-B.Now the fun starts.  If you put their 100 ohm load between A and B you will get a current flowing, but now you have to apply your circuit analysis techniques.  Which I did some time ago but have mostly forgotten   So if you will forgive me I'll have get the books our and come back to this, probably at the weekend.Meantime if there's anyone else who remembers this stuff please enlighten us

This site has a good explanation of how to do this type of problem.https://en.wikibooks.org/wiki/Circuit_Theory/One_Port_DevicesBasically you start at the innermost part of the circuit and simplify by calculating an equivalent resistance and voltage source.In this case,  you start with the 20V and 150 Ohm across the 10V which, as David points out is equivalent to just the 10V.Next we move on to the 10V being divided by the two 150 Ohm resistors. With no load on the output, we would measure 5V. With the 10 V shorted, the circuit becomes two 150 Ohm resistors in parallel or 75 OhmsThis gives us an equivalent circuit of 5V with a 75 Ohm series resistor.Putting  the 5V in series with this gives us 10V in series with 75 OhmsWith no load the output of this is, as David said, 10VWith 100 Ohms we now have a resistor divider of 75 and 100 Ohms so we should have a voltage of about 5.7V

Elizabeth...you make it look so easy