Hoping someone is great at business math. Are you? Please assist me.?

Question

Im trying to find the equasion for these. Answers will help me with homework but nto test. Please explain a little. (see im not a cheater, which is rare I know.) thanks in advance.

1) Ron Prentice bought goods from Shelly Katz. On May 8th Shelly gave Ron a time extension on his bill by accepting a 3,000, 8%, 180 day note. On August 16, Shelly dicounted the note at the bank at 9%. what proceeds does shelly katz receive?

2) On May 12, Scott Rinse accepted 8,000, 12%, 90 day note for a time extension of a bill for goods bought by Ron Prentice. On June 12 Scott discounted the note at Able bank at 10%What proceeds does scott receive?

Answer 1

3000 plus 8% during 180 days will be worth, at the end of the period,
3000 * (1+.[08 *180/360]) = 3000 * 1.04 = 3120
Now, which amount X, will be worth 3120 if invested at an annual rate of 9%?
That is X * (1+[.09*180/360])=3120
then X= 3120/(1+[.09 * 180/360]) = 3120/1.045=2985
You should be able to solve by yourself No 2