Identifying the Largest Increase in Ticket Sales

Below is a line graph displaying the number of tickets sold for a school play over a week:

Line Graph:

Day 1: 10 tickets
Day 2: 15 tickets
Day 3: 20 tickets
Day 4: 30 tickets
Day 5: 25 tickets
Day 6: 35 tickets
Day 7: 45 tickets

Based on the graph, which day had the largest increase in tickets sold compared to the previous day?