Answer:
A total of 53 sales to qualify for bonus
Explanation:
In the first week, they required a sale of 20 tickets to recieve a bonus.
In subsequent weeks, they require a sale of (n + 3)
Where n = number of sale the previous week
Week 2, they'll require n + 3 = (20 + 3) sales = 23 sales
Week 3 = 23 + 3 = 26 sales
Week 4 = 26 + 3 = 29 sales
Week 5 = 29 + 3 = 32 sales
Week 6 = 32 + 3 = 35 sales
Week 7 = 35 + 3 = 38 sales
Week 8 = 38 + 3 = 41 sales
Week 9 = 41 + 3 = 44 sales
Week 10 = 44 + 3 = 47 sales
Week 11 = 47 + 3 = 50 sales
Week 12 = 50 + 3 = 53 sales
At the end of week 12, they require a total of 53 sale to qualify for bonus