Answer:
1/3
Explanation:
Total number of people who play sports in the Algebra 2 class:
![21 - 9 = 12](https://img.qammunity.org/2022/formulas/mathematics/high-school/8r0k4c9cbf0rt1uwuuedgktv0cp1r8xrv6.png)
If there are 10 students who play Basketball, there are 2 students who ONLY play Baseball. If there are 9 students who play Baseball, there are 3 students who ONLY play Basketball.
So the number of students who play BOTH sports is:
![12 - 2 - 3 = 12 - 5 = 7](https://img.qammunity.org/2022/formulas/mathematics/high-school/we8kn3ikzg6nswi9l91b1wqab8yeg50wmb.png)
If 7 from the 21 Algebra 2 class students play BOTH sports, the probability is:
![P = (7)/(21) = (1)/(3)](https://img.qammunity.org/2022/formulas/mathematics/high-school/sanz5ju0a8odjnqvkx2m9xyd523se8fwx1.png)