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 conneted.

The faces 1 and 2 form a capacitor out of which , 1 s conneted to V volts and 2 is grounded . Similarly, faces 3 and 4 form a 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 `((epsilon_(0)A)/(d))V`
Net charge on plate B is equal to sum of charges
on faces 2 and 3 , which is equal to `- (( 2 epsilon_(0)A)/(d))V`
Net charge on plate C is `((epsilon_(0)A)/(d)) V^(-)`