/sci/ - Science & Math

Dumb question time.
I'm trying to do some diode circuit analysis, the blue is the constant voltage drop model where I assumed that the diodes were on so they turn into a 0.7V source. My question is about the parallel arrangement you see at red (1) and (2).
I can see why it went from 5.0V to 3.3V as there is a voltage drop across the 1.7K resistor on the top line but I don't understand why we needed to subtract the two voltage sources on the bottom line (0.7V and 1.0V) rather than add them.
I know this is probably some basic circuit analysis stuff, however, my teacher wasn't really the best (espescially during zoom university) so uhh, pretty lost here...