The relation is not a function. Domain: 5, 6; Range: 6, 7.
Work Step by Step
This is not a function because $x=5$ corresponds to both $y=6$ and $y=7$. For a relation to be a function, it has to relate only a single value of $y$ for each $x$. 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.