I was confused on how to answer these questions, I did something wrong and I am not sure where I messed up. Can you show me all the steps please.

Two 4.0 g beads are equally charged and placed 30 cm apart. When released, both beads begin to accelerate at 100 m/s2 under their mutual repulsive force. Determine the magnitude of the charge on each bead. In the diagram below, the net force on the 1.0 pC charge is equal to zero. Determine the sign and magnitude of the unknown charge Q. 4.0 cm --1