Answer:
18
Explanation:
The ~ indicates that ∠ABC is similar to ∠QRS. In other words, their proportions are the same, even if their size is different.
So AB has the same proportions as QR. 4 can be multiplied by 2.25 to get to 9. So multiply 8 by 2.25 to get n.
8 * 2.25 = 18 so n = 18