Find the charge on each plate given area of each plate is A and separation between two consecutive plates is d.

Explanation

Let the plates are A , B and C . This is an arrangement of two capacitors . First we identify how the capacitors are connected .

The faces 1 and 2 from a capacitor out of which 1 is connected to V volts and 2 is grouded . Similarly faces 3 and 4 form capacitor out of which 3 is grounded and 4 is connected to V volts . The arrangement is 2 capacitors in parallel.
So , we have Q = CV `=((epsilon_(0)A)/(d))V`
So , net charge on plate A is `((epsilonA)/(d))A `
Net charge on plate B is equal to sum of charges
on faces 2 and 3 which is equal to `-((2epsilon_(0)A)/(d))` V
Net charge on plate C is `((epsilon_(0)A)/(d))` V