This question 19 Part (c) is not so hard.
Step 1. Recognise that for each mass on the string, the tension force is the same. Also recognise that the forces on the system are both masses experience the force of gravity vertically downwards.
Step 2. Decompose the force of gravity on each mass into orthogonal vectors, one vector that is normal to the inclinded plane, and another vector that is parallel to the inclined plane.
Step 3. At equilibrium, the two vectors that are parallel to their respective inclined planes will be equal. If the system is not at equilibrium, then they will not be equal, and there will be a net force on the system making it move.
At equilibrium, m_{1}g sin θ = m_{2}g sin 2θ where m_{1} = 3 and m_{2} = 2
next you are going to need the following trigonometric identity:
sin 2θ = 2 sinθ cosθ
Do you think you can do the rest of the calculation now?