How can i find the acceleration? (rope and grinder have no weight) *** sorry for my english

The main formula to be used here is

                       Force = (mass) x (acceleration).

We'll get to work in just a second.  But first, I must confess to you that I see
two things happening here, and I only know how to handle one of them.  So
my answer will be incomplete, but I believe it will be more reliable than the
first answer that was previously offered here.

On the right side ... where the 2 kg and the 3 kg are hanging over the same
pulley, those weights are not balanced, so the 3 kg will pull the 2kg down, with
some acceleration.  I don't know what to do with that, because . . .

At the same time, both of those will be pulled up by the 10 kg on the other side
of the upper pulley.

I think I can handle the 10 kg, and work out the acceleration that IT has.

Let's look at only the forces on the 10 kg:

-- The force of gravity is pulling it down, with the whatever the weight of 10 kg is.

-- At the same time, the rope is pulling it UP, with whatever the weight of 5 kg is ...
that's the weight of the two smaller blocks on the other end of the rope. 

So, the net force on the 10 kg is the weight of (10 - 5) = 5 kg, downward.

The weight of 5 kg is (mass) x (gravity) = (5 x 9.8) = 49 newtons.

The acceleration of 10 kg, with 49 newtons of force on it, is

     Acceleration = (force) / (mass) = 49/10 = 4.9 meters per second²

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