## Thinking Mathematically (6th Edition)

$\left\{1, 2, 3, ..., 28, 29, 30\right\}$
$N$ is the set of counting or natural numbers. Natural numbers are $1, 2, 3, ...$ The value of $x$ is less than or equal to 30. This means that the possible values of $x$ are $1, 2, 3, ...28, 29, 30$. The roster method lists down all the elements of the set. Thus, writing the given set using the roster method gives: $\left\{1, 2, 3, ..., 28, 29, 30\right\}$