Three point charges 2mu C,-3mu C and -3 mu C are placed at vertices of an equilateral triangle with side 20cm. What must be sign and magnitude of charge to be placed at midpoint M of side BC to keep charge at A at equilibrium?

Here you should specify the vertices of the triangle ABC if BC is line joining - 3 and minus 3 then you can I get the forces of attraction between -3 - 3 and 22 the repulsion between two and a charge q sister distance can be calculated you can get the answer by equating the forces that is resultant force with the required for us to keep it in equilibrium that is equal and opposite force that will give the charge to be positive and magnitude9root3÷4