Sesame Street to help us out..
X is the third least common letter in the alphabet, so if you are struggling with this letter for the challenge you now know why.
X is also used for an independent variable in math. Also an axis.
Apparently a lot of people want you to sign by the X. I have also heard X marks the spot. Whatever the case might be this is my blog post on the letter X. I will be back soon with a new post.