To the problem:

So, looking at the circuit it's obvious there are 4 nodes, so will expect 3 equations for 3 unknowns. I will consider the bottom node as reference. I tried other circuit configurations with different reference but it didn't help.

But one of the nodes, Va, is known to be 10V. I'm not exactly sure but I believe this means that since now it's only 2 unknowns, that we only need 2 equations.

Node a:

-iΔ + (Va-Vb)/10 + (Va-Vc)/30 = 0

Node b:

(Vb-Va)/10 + Vb/40 + (Vb-Vc)/20 = 0

Node c:

(Vc-Va)/30 + (Vc-Vb)/20 +/- .... = 0

I made 3 equations because I believe there should be a supernode around Vc and reference, leading to 2 eqn's, but I've never seen a problem before with a supernode that connects a regular essential node to reference, or if that even makes sense. In the first equation, I'm not sure if -iΔ is correct, but I'm much more confident in that than the last one, where I didn't even write anything for the CCVS..

This is my absolute best. I know I am suppost to make a substituation for iΔ, but I don't know what iΔ since there is not resistance, and that doesn't help for replacing 20iΔ.

I'm looking for feedback based on what I did wrong. Then I'll take that and try to solve.

MOD EDIT: Inserted image into post body.