Solving a Tricky Physics Pulley Problem: Finding M2 with Tension and Mass M1

[Arman777]

I didnt understand you

 

[Arman777]

no problem, but shouldn't you be right if we are solving for M2? all the m2 should be on the LHS right?

I diddnt understand you

 

[haruspex]

Leave M2 alone in this equation.

That might be causing some confusion. You mean, manipulate the equation so that M2 is alone on one side of the equation, and does not occur on the other side.
(Leaving it alone would mean not doing anything with it.)