No, it's not.
Let [tex] x [/tex] be ANY multple of 10. This means that [tex] x = 10k, k \in \mathbb{Z} [/tex].
Now, if we divide this multiple of 10 by 2, we get
[tex] \cfrac{x}{2} = \cfrac{10k}{2} = 5k [/tex]
So, it is true that if you divide any multiple of 10 by 2 the answer is always a multiple of 5, but it doesn't mean that it has to be 5 itself.
