1. The problem is to find the sum of 68, 48, and 15. 2. The formula for addition is simply adding the numbers together: $$a + b + c$$. 3. Substitute the values: $$68 + 48 + 15$$. 4. Add the first two numbers: $$68 + 48 = 116$$. 5. Add the result to the last number: $$116 + 15 = 131$$. 6. Therefore, the sum of 68, 48, and 15 is 131.