Peter can buy 5 juice bottles for $10 or 6 juice bottles for $12. how much do you think he would pay for 7 juice bottles?

He would pay $14. Each juice bottle costs $2, so 7 bottles cost $14. 

This one is really easy, once you simplify the question.
5 bottles for $10 would be $2 each.
6 bottles for $12 would also be $2 each.
Therefore, 7 bottles would be $2 x 7, which is $14.