Your question is calling the figure ABCD, but the image is showing PQRS
Using the letters that you wrote:
Because the figure was only rotated and not scaled , the sides with the same letters would still be the same
So AB would be the same as A'B' ( Length of AB = Length of A′B)
and
BC = B'C'
CD = C'D'
AD = A'D'
Or by the picture:
PQ = P'Q'
QR = Q'R'
RS = R'S'
PS = P'S'
Let the number of rows be = r
Let the number of seats per row be = s
we know that the number of seats is 126.
So,
..... (1)
As given, there are five more seats per row than the number of rows, so we can say that:

Putting this in equation (1)





r=-14 and r=9 (neglecting the negative value) we get r=9
And s=r+5
so, s =9+5=14
Hence, there are 5 rows and 14 seats per row.
This is not my work but i hope this can help you with your problem
https://answers.yahoo.com/question/index?qid=20120518194118AAhi738