3 Tough Physics Questions?

[Blizz]

Please help me out here, been working on physics for several hours now and understood the majority of the questions but these 3 I just cant figure out.

1. http://tinypic.com/view.php?pic=qn69t5&s=3
The two blocks are sliding down the incline, what is the tension in the string (in Newtons)

2. http://tinypic.com/view.php?pic=6qwruo&s=3
The coefficient of kinetic friction between the 2 kg block and the table is .25. What is the acceleration of the 2 kg block (in m/s^2)

3. http://tinypic.com/view.php?pic=2r3e1wo&s=3
Find an expression for the magnitude of the horizontal force F in the figure for which m1 does not slip either up or down along the wedge. All surfaces are frictionless.

Please explain your answers as I have to understand this material for the test. Thanks for your help.