Answer:
Hi,

Explanation:
The statement "a:9 = 18:a" represents a proportion.
To find the positive value of "a," you can cross-multiply and then solve for "a." Here's how you can do it:
a:9 = 18:a

Cross-multiplying:
a * a = 9 * 18

Now, to find the positive value of "a,"

So, the positive value of "a" is approximately 12.73.