Answer: $90
Explanation:
The formula we use to find the simple interest is given by :-
, where P is the principal amount ,r is the rate of interest ( in decimal) and t is the time period ( in years).
Given : Dante borrows $500 from his older sister and agrees to pay her 6% simple annual interest.
i.e. P=$500 ; r=6%=0.06
Now, the simple interest Dante will owe at the end of 3 years will be :-

Hence, Dante will owe $90 as interest at the end of 3 years.