Answer: x=4
Steps: (I am assuming your question has a typo in it and by "c" you meant "x")
The rational expression equals zero

only when the numerator equals 0 (the denominator cannot ever be zero):

and that happens only for x=4
It is Arithmetic. It follows a pattern of divide by 2, which gives it the name "Arithmetic" and you can think of it as "Arithmic," which sounds like rythm. It follows the rythm of Divide by 2. Hope this helps, and let me know if I made any mistakes!