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00:34order of operations and substitution in math before watching this video.
00:41What is the value of 3 times a plus 5 when a equals 6? Enter your answer in the box.
00:49To solve this problem, we need to know about substitution and about the order of operations.
00:54We'll begin by using substitution. First, we rewrite the expression by replacing the
01:01multiplication x with an asterisk. Then we rewrite the expression by substituting the letter a with
01:10the number 6. That gives us 3 multiplied by 6 plus 5. Next, we need to know which operation to do first.
01:18Here's a reminder of the order of operations. For elementary school, they're free boxes. The order of
01:24operations tells us which order to do things in. We start with the top box, then do the middle box,
01:30then do the bottom box. The order is parentheses, then multiply and divide, then add and subtract.
01:38One way to remember what words go in each box is to use a memory aid like this sentence.
01:43Please make drinks and sandwiches. The first letter of each word in the memory aid is the same as the
01:49first letter in the order of operations. We also write in a reminder that if both are present,
01:55then do the left ones before the right ones. There are no parentheses, so we'll move down to the red
02:00box. There's a multiplication operation here. 3 times 6 equals 18. We bring down the 5 and the addition
02:08symbol. There's only one operation left, which is addition. 18 plus 5 equals 23.
02:1523. The value of this expression, when a equals 6, is 23. Thanks for your attention.
