my school taught an incremental method, where you basically just chop and gather pieces of the circuit until you have your circuit made
im going to do this in my head, cuz im to lazy to get a calculator, so here it goes:
So for node 1, you have 90V accross 15K, So you could model this as a 4mA(90V/15kOhm) current source in parrallel with a 15k Resistor.
So now we have the 15k and 10k in parallel with a 4mA current souce, which is the same as the 4 mA current source and a 6k resistor in parrallel 1/(1/10k+1/15k)
Then we rebuild this new "source" as a voltage source in series with a 6k resistor. So we have a 4mA x 6k voltage source = 24V.
So now we have removed R1 and R4 and V1 and can replace that chunk with a Voltage source of 24V and 6K series resitance. Since this is in series with R2, we can model the resistance as 10k
Boom, now we have the block of (24V in series with 10K) in parrallel with R5. And we have removed R1,R2 and R4
Just continue this process until you have removed everything.