Solving for Velocity on a Pulley System

[RoyalFlush100]

Homework Statement

In the picture below.

Homework Equations

Velocity on a pulley = (velocity on left rope + velocity right rope)/2
Pulley A and C have 0 velocity.

The Attempt at a Solution

By inspection the right sided rope on pulley A is 120 mm/s going up.
After that is when I get confused. Pulley B and D are in motion, so I don't see what else to do from here.

 

[haruspex]

left sided rope on pulley A is 120 mm/s going up.

Looks like down to me.

Velocity on a pulley = (velocity on left rope + velocity right rope)/2

So apply that to each pulley in turn, working from the left.
What does it tell you about the velocity of the second rope segment (the one on the right of pulley A)?

 

[RoyalFlush100]

Looks like down to me.

So apply that to each pulley in turn, working from the left.
What does it tell you about the velocity of the second rope segment (the one on the right of pulley A)?

Yeah, I meant the rope to the right.

But still, we don't know vB, meaning we'd have:
vB = (150+vBR)/2
Where vBR is the velocity on the right of pulley B.
By inspection vCL = -vBR

But from here, I'm not sure how to proceed since vB is not 0

 

[haruspex]

Yeah, I meant the rope to the right.

Ok.
I feel your notation is going to get a bit confusing since you will have two names for the same rope.
I'll just label them and their velocities a to e across the top, and the segment left of the lowest pulley is f.
You already have a=-b.
Next, look at pulley C. What equation can you write for that? Then move on to pulley B.
You don't need to solve these equations, determining velocities, as you go along. Just get all the equations written first.