The seats in the theater follows the sequence given by:
7,9,11,..
This is an arithmetic sequence which follows an explicit formula given by:
an=a+(n-1)d
where:
a=first term
d=common difference
but
a=7 and d=9-7=2
thus
an=7+(n-1)2
an=7+2n-2
an=2n-5
Thus the number of seats in nth row is:
an=2n-5