When multiplying monomials with the same base, meaning the same letter, we need to follow the procedure below:
1 - multiply the numerical parts;
2 - repeat the letter;
3 - add the powers of the letter.
With this in mind we can solve the product as shown below:
[tex]9\cdot a^{(5\text{ + 5)}}\text{ = 9}\cdot a^{10}[/tex]