Determine the sum of 11 and 9: $11+9$

Step 1 ：Determine the sum of 11 and 9: \(11+9\)

Step 2 ：This is a simple addition problem. We need to add 11 and 9 together.

Step 3 ：sum = 20

Step 4 ：Final Answer: The sum of 11 and 9 is \(\boxed{20}\)