First of all, if there are at least 70 seats, there must be at least 9 rows. (9*8 =72, which is required to have minimum 70 seats).
And, maximum 150 seats are there, so 150/8 = 18.75, i.e. 18 rows can be there at maximum.
So, the actual number of rows can be between 9 and 18. We can say that possible number of rows can be 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18.