 Order of operations. In mathematics, we have the basic operations of addition, subtraction, multiplication, and division. We also use parentheses for grouping, raise numbers to powers, and evaluate roots. When we have a combination of these in a problem, or even have more than one addition, subtraction, multiplication, or division sign in a problem, we need to know what to do first. If we perform the operations in any order we choose, two people may come up with different answers to the same problem. In mathematics, there can only be one correct answer. Just as we have a set of rules that we follow when we play a board game, we also have set rules that we follow when we do math. Consider the following situation. You are paid a weekly salary of $400 and you also receive a commission of $10 for every TV you sell. On average, you sell 24 TVs a week. What is your average weekly earning? The problem says we should get $400 plus 10 times $24. How much are we paid? Is it the one on the left or the one on the right? It's the one on the right. Common Sense tells us that we will receive $640 instead of $9,840 because we have a real life situation to relate to this. What if we did not? How would we evaluate $400 plus 10 times 24 without knowing what the numbers refer to or what the situation is? It is because of the confusion that problems like the one above could create that long ago mathematicians adopted the rules that we still follow today. This set of rules is called the order of operations. We will use the order of operations to solve the problem 3 to the power of 2 plus 24 divided by 3 times 2 minus 4 minus 2. Do the operation inside the parentheses first. Next, evaluate the exponents or roots. Do multiplications and or divisions starting on the left and working to the right. Last, do additions and or subtractions again starting on the left and working to the right. As an aid in remembering the steps, you may use this sentence. Please excuse my dear Aunt Sally. P stands for parentheses. First, do what is inside the parentheses. E stands for exponents or roots. Second, calculate the powers and roots. M and D stand for multiplication and division. Third, do all the multiplications and or divisions beginning at the left and working to the right. A and S stand for addition and subtraction. Fourth, do all the additions and or subtractions beginning at the left and working to the right. Let's try some examples. This problem contains only multiplications and divisions. Since divisions and multiplications rank equally in importance, they must be worked in order beginning at the left and working to the right. This problem contains only additions and subtractions. Since additions and subtractions rank equally in importance, they must be worked in order beginning at the left and working to the right. Now try a problem involving addition, subtraction, multiplication and division. The correct answer is 89. Here's how it's done. Now try a problem involving addition, subtraction, multiplication, division, parentheses and exponents. Remember to use please excuse my dear Aunt Sally. Now it is time for you to practice some problems on your own. Evaluate the following 10 problems and see how you do. Pause the video here. Press play once you're done with all of the problems. You have completed this lesson on the order of operations.