Question 231291
Hello, 
We should start with: What does "Undefined" mean?

It means a number cannot be divided by zero. 
So the only answer for this is y = 6
To better understand why you can't divide by zero, let's set up a real example. 
If there no candy and 6 kids. How many pieces of candy will the kids get? 
Right. Nothing.   It would look like this 0 candy divided by 6 kids. 
Now, let's suppose there is 6 pieces of candy but no kids. 
How many pieces of candy will no kids get? See it doesn't make sense, that's why it's called undefined. 
RJ Toftness
Author "Unlock the Mystery to Math" 
www.math-unlock.com