$7$ is a prime number, so its only factor other than itself is $1$.

Their greatest common factor is $1$. Can you find their least common multiple?

To find the least common multiple, try finding multiples of $15$ and checking
whether they are also multiples of $3$ and $9$.

The least common multiple is $45$. Try finding the greatest common factor.

$10$ is a factor of both of these numbers.