solution:

We go through each careful drawing and write out equations with the unknown tensions and acceleration.

Block 1:

Disc 1:

Block 2:

Disc 2:

Block 3:

We now have 5 equations and 5 unknowns. Now for the fun part!
Plugging numbers into (20), we get:

Now we equate this to equation (15) and plug in numbers:

Now we equate this to equation (11) and plug in numbers:

You get the picture setting this equal to (6):

Finally we get to setting this equal to (2):

Plugging in 'a' in equations (29), (27), (25) and (23) give: