If you deposit $800 in a savings account that earns simple interest at a pate of 1.5% per year, how much interest will you have earned after 5 years?

The answer to that is $60.
Working:
1.5% of $800 is 
1.5% x 800 = $12
That means every year $800 of deposit will earn you $12 of interest at the rate of 1.5%.
To find the total interest earned in 5 years multiply the interest of 1 year with 5.
 $12 x 5 = $60