Hello guest, welcome to Web.2.0 =)
This would be the formula for finding compound interest.
P would equal how much you borrow or deposit.
r would equal a decimal of your rate of interest
t would equal how many years your borrowed or deposited value has been in/out for
n would equal how many times the interest was compunded in a year
A would equal the ammount of money and interest owed/accumulated in n years
Sorry this is late '=)
Well the first question is simple! find the equation that could equal 1021 dollars, note in A at the end of 13.25 there is an s, this s is an unknown number that 13.25 will be multiplied by. so if we subtract 650 from 1021 we will find how much more we need. 1021-650= 371. so divide 650 by 13.25 and you will find S