Solution
= Solution
\b[This is an <equivalence relation>.] The difference $x-x=0$ is an even <integer>, proving <reflexivity>. If $x-y=2k$ then $y-x=-2k$, proving that the relation is <symmetric>. If $x-y=2k$ and $y-z=2\ell$ then $x-z=2(k+\ell)$, proving <transitivity>. Its <equivalence classes> are the translates $x+2\mathbb Z$; two <real numbers> need not be <integers> themselves to belong to the same class.