How charge on Bbecomes q/2 and on C3q/4how???????

First consider two points at which same charge `q` is present such as B and CBring a uncharged body to point B .The charge will be equally distributed between two pointsSo it will be (B+A)/2 since charge on B is qAnd charge on A is 0 :. Charge on both B and A will be q/2Now bring newly charged A to point CNow the same thing happensCharge will distribute equally b/w the two points A+C/2(q/2 +q)/2:.3q/4