If there are 70 chairs but only 20 rows then that means he will have to set up 3.5 chairs per row, or Brook could set up 14 rows with 5 chairs in each row.
Srry if that didn't help but that's what i got from that.
Answer:
The first, third and last one are true
5-4 //jzbbxbxbzbbsjd jsjdjcn ñandú
Take a picture of the problem on PhotoMath and it will break down all of your steps.