The relation is a function. Domain: 4, 6, 8; Range: 5, 7, 8.
Work Step by Step
Since there is only one $y$ for each $x$, the relation is a function. The Domain is the set of all $x$'s, or what "you start with". The Range is the set of all $y$'s, or what "you end up with", after each member of the Domain has been changed by the function.