Answer: 20 tickets
Explanation:
From the question, we are informed that Shelby sold 75 raffle tickets for the school fundraiser over a 3-year period while Kelly sold 15 less tickets than Shelby. This means that the number of tickets sold by Kelly is:
= 75 - 15
= 60 tickets
The number of tickets sold by Kelly each year on average will be:
= Number of tickets sold / Number of years.
= 60/3.
= 20 tickets
over the last 3 years