Final answer:
Zechariah hit a total of 1539 baseballs last year, having attended school for 171 days and hitting an average of 9 baseballs per day.
Step-by-step explanation:
To calculate how many total baseballs Zechariah hit last year, we first need to find the number of days he actually attended school. Since the school year is 180 days and he was absent for 9 days, he was present for 180 - 9 = 171 days. Then we can calculate the total number of baseballs by multiplying the number of days he attended school by the average number of baseballs hit per day. So, Zechariah hit 9 baseballs per day × 171 days = 1539 baseballs in total over the school year.