Need with these 2 problems i’m pretty sure i got the first one right but i don’t know how to do the second one and

Since APR interest is a simple interest rate, we are going to use the formula for calculating simple interest: 
where 
is the final amount after  years
is the initial investment 
is the interest rate in decimal form 
is the number of years 

Mathematical steps for solving the problem:
We can infer from our problem that you are going to invest $800-$640=$160 in your savings account, so . To convert the interest rate to decimal form, we are going to divide the rate by 100%
. Since you are leaving the money in your savings account for a year, . Lets replace those values in our formula:






We can conclude that  your total savings after buying the refurbished laptop are: $167.2