To me, this is more of an engineering studies question than a physics question, but I'll give it a shot anyway.
Since the stick is in equilibrium, the clockwise torques must equal the counter-clockwise torque.
In the diagram I made, the clockwise torques were the force at 10 cm and the mass (centred at 20 cm) and my counter-clockwise torque was the mass centred at 70 cm. These may be opposite in your diagram, you'll still get the same answer.