Answer:
6
Step-by-step explanation:
Chords within a circle are proportional. Proportional means that they form equal ratios. To solve for y, set up a proportion.
The ratios we will create will be
where each long and short form an angle.
So write:

To solve, cross multiply numerator with denominator.
12(4) = 8(y)
48=8y
6=y
→ 
8 and 10 can both be divided by 2. So, 8 ÷ 2 is 4 and 10 ÷ 2 is 5.
Hope this helps :)
Answer:
D
Step-by-step explanation:
You are always able to do better, and Fiona needs to reflect
The answer should be 9sqrt2 because the equation for finding the legs on a 45-45-90 triangle is hypotenuse/sqrt2.