To check the sum of 27, 15, and 12 using addition, you should start by adding the numbers together in a step-by-step manner.
First, add the first two numbers:
27 + 15 = 42
Next, take this result and add the third number:
42 + 12 = 54
Therefore, by performing the addition step by step, we find that the total sum is 54. This method of checking ensures accuracy and confirms that the value is correct. If you were to add in a different order, such as 15 + 12 first, you would still arrive at the same total when combined with the other number.