Is it

or

?
both start out the same, just remember what you do to one side you have to do to the other, so subtract both sides by 1/4, then you want to get y alone, so either divide or multiply the 3 on both sides! let me know which it is and I can help you out more
[edit] it's the second, and not going to use cross multiplication.
added a picture that walks you through it :)
Answer:
√96
Step-by-step explanation:
halve the diameter to set up the pythagorean theorem
2²+b²=10²
4+b²=100
-4 on each side
b²=96
square root each side
b=√96
it could the be further simplified to 4√6
Answer:
1
-12
3
6
Step-by-step explanation:
the answer to the problem is 1/4