Plz help me out, this is from a study guide for my test today! thank you!

A) if $50000 is invested in a bank account that pays 9.3% of interest compounded on a six-monthly basis, how much money will be in the account after 3 and 12 years? b) if matusalen's father had put $2.0 in the bank when he was born and there, how long would matusalen have had to his death (969 years later) if the interest was 7% per year composed each month and weekly?

How many $20 bills do you need to have to make $280

The final cost of a sale is determined by multiplying the price on the tag by 75%. which best describes the function that represents the situation?