I assume that all the strings are tight and the whole system is stationary i.e. the balls B and C are in equilibrium.Originally Posted byThePerfectHacker

Let the tension in the part AB of the string be (I don't know how to make overhead arrow, just assume it a vector). Its direction is from A to B. represents the same tension with direstion reversed.

Equations are

WEIGHTS ARE DIRECTED DOWNWARDS

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