Please answer

Let the number of rows be N and M be cars per row.

Total number of cars at any time t = NM

M+3 then N-1.

M-3 then N+2.

But the total number cars are fixed at that time in the parking place.

Hence,

(M+3)(N-1) = NM

3N - M = 3 ...............(1)

and 

(M-3)(N+2) = NM

2M - 3N = 6 ............(2)

Solving (1) and (2), 

N=4, M = 9.

Total number of cars at that particular time = 36

Regards,

Team,

TopperLearning.