4.OA.B.4 math practice. Learn by doing.

Add the digits: $9 + 9 = 18\textsf{.}$

$36$ is a multiple of $9$: $9\textsf{,}$ $18\textsf{,}$ $27\textsf{,}$ $36\textsf{,}$ $\ldots$

$15$ has factors $1\textsf{,}$ $3\textsf{,}$ $5\textsf{,}$ and $15$, so it is composite.

The last digit of $130$ is $0\textsf{,}$ so $130$ is divisible by $10\textsf{.}$

Four $8\text{s}$ make $32$: $8\textsf{,}$ $16\textsf{,}$ $24\textsf{,}$ $32\textsf{.}$

$29$.

The last digit of $84$ is $4\textsf{,}$ which is even, so $84$ is divisible by $2\textsf{.}$

Five $6\text{s}$ make $30$: $6\textsf{,}$ $12\textsf{,}$ $18\textsf{,}$ $24\textsf{,}$ $30\textsf{.}$