Answer
The number is $63$.
Work Step by Step
To solve this problem, we need to translate the problem into an algebraic equation.
"The product of $5$ and a number" means "$5x$."
"Decreased by $9$" means to subtract $9$.
"Is $306$" means "$ = 306$."
Now, we can put all the pieces together into an equation:
$$5x - 9 = 306$$
We add $9$ to each side to move the constants to one side of the equation:
$$5x = 315$$
Divide each side by $5$ to isolate $x$:
$$x = 63$$
The number is $63$.