Answer:
The answer to your question is 60 days
Explanation:
Data
Middle school every 15th day
High school every 20 day
When will the schools serve pizza again?
Process
1.- Calculate the Least Common Factor
15 20 2
15 10 2
15 5 3
5 5 5
1 1
LCF = 2 x 2 x 3 x 5
= 60 days
2.- Conclusion
In 60 days Middle school and Highschool will serve pizza again.