Trying to understand how voltage \$ V_{D1} \$ is found.
Here's the original circuit with solution:
Here's how I think it can be redrawn, basically the grounds are just one node:
So to find voltage \$ V_{d1} \$ one first considers what's voltage at point 1, positive side of \$V_{d1}\$ right?
Well, at point 1, voltage is what? \$ -10K \times 1.33mA? \$
How about voltage across 5k resistor? Point 1 is between 10k and 5k resistors...
For point 2 it's 0, since the node of that point is connected to ground, right?