Help Finding the Tension between 2 Masses

[ttk3]

Three blocks on a frictionless surface are connected by massless strings, with M1 = 1.10 kg, M2 = 2.80 kg, and M3 = 3.50 kg. Due to the force F acting on M3, as shown, the system accelerates to the right. Given that T1 is 2.90 N, calculate T2.

I found the acceleration of the problem using F1 = m1 (T1 / (M1 + M2)). Where do I go from here?

 

[learningphysics]

So is T1 between M2 and M3, and T2 between M1 and M2?

I don't understand how you got the acceleration... can you describe or upload a picture?