Answer:
a = 1
Step-by-step explanation:
First, you subtract 6 from both sides and you end up with a² = 1. Since one cannot be squared or square rooted, a = 1. I hope this helps!
The unknown factor is the divide sign
The median or middle would be 1.5, since in the middle are 2 numbers 1, and 2. You would add them together and divide them by 2 and get 1.5