In the next olympics the united states can enter four athletes in the divivng competition. how many different teams of four divers can be selected from a group of nine divers?

Pls! does anybody know a shortcut for answering these types of questions in the future?

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 jamie pay at the end?

Consider the function f(x)=-5x+3 what is f(-2)