What two numbers add up to 18?

To find two numbers that add up to 18, we can set up an algebraic equation. Let's call the two numbers x and y. The equation we need to solve is x + y = 18. Since we are looking for two numbers that add up to 18, there are multiple possible solutions. For example, one possible pair of numbers that add up to 18 is 10 and 8, as 10 + 8 = 18.