This variation on Qu121 allows an explicit solution to be calculated. Where the previous puzzle might be regarded as slightly tricky, this is straightforward in the sense that there are no unexpected tricks---it is purely a question of carefully applying methods in statics.
A pulley arrangement consisting of a fixed pulley A, a fixed double pulley B, and a free pulley C is attached to two masses D and E as shown in the diagram. D is twice the mass of E, the pulleys are light and frictionless, and the ropes are light and inextensible. The pulleys are very small in comparison to their separation. The system is initially held in a position shown. The angle rope CA makes to vertical is θ, and the angle ropes CB make to the vertical is φ. The system is released. Without complicated algebra, determine the angle θ when the system is in equilibrium. Hint---use a symmetry argument.