Can you guys help please

Which of the following answers is 5/25 simplified? 1/5 5/5 2/5 1/25

Jamie went to home depot.she bought 25 bags of soil that cost $9 per bag.she bought 15 pots at $8 each,and she bought 23 bags of pebbles at $15 each.she used a coupon that gave her $5 off for every 100 dollars she spent.how much did jame pay at the end?

Another type of subtraction equation is 16-b=7. explain how you would sole this equation then solve it.