1. The problem is to find the sum of $x$ and $y$ given $x=9$ and $y=8$. 2. The formula for the sum of two numbers is $x + y$. 3. Substitute the given values into the formula: $9 + 8$. 4. Calculate the sum: $9 + 8 = 17$. 5. Therefore, the sum of $x$ and $y$ is $17$.