Answer:
28
Step-by-step explanation:
There were 7 chairs in each row, now they add three more to each row so now there's 10 chairs per row. There were 56 chairs altogether previously but now they need 5 times more so 56 times 5 equals 280. so with ten chairs per row and 280 chairs in total: 280/10 = 28. You'll need 28 rows
