Answer:
The possible number of rows can be 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, or 42.
Explanation:
First of all, if there are 70 seats, there should be 9 rows. (9*8 =72, which has 70 seats). And, 340 seats are there, so 340/8 = 42.5, i.e. 42 rows can be there at maximum. So, the actual number of rows can be between 9 and 42. Therefore the possible number of rows can be 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, or 42.
Hope this helps. :)