1. The problem is to find the sum of the numbers 15, 8.65, and 5. 2. The formula for addition is simply adding all numbers together: $$\text{Sum} = a + b + c$$ where $a=15$, $b=8.65$, and $c=5$. 3. Substitute the values: $$\text{Sum} = 15 + 8.65 + 5$$. 4. Perform the addition step-by-step: - First, add 15 and 8.65: $$15 + 8.65 = 23.65$$. - Then add 5 to the result: $$23.65 + 5 = 28.65$$. 5. Therefore, the final answer is $$28.65$$. This means when you add 15, 8.65, and 5 together, you get 28.65.