What happens when you see 42 (17 – 15) / (3 + 1) – 5 ? What do you do first? The mnemonic PEMDAS or Please Excuse My Dear Aunt Sally can help you remember the order of operations: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction. If your expression doesn't have every type of operation, the order of operations is still the same. If it is missing one, just skip it and move on to the next operation. Which operation is done first to evaluate this expression: 5 + 7 x 2 - 9

The operations done first are:

a)  42 (17 – 15) / (3 + 1) – 5 ; (17 -15) or (3 + 1) (parenthesis) are done first

b)  42 (17 – 15) / (3 + 1) – 5 ; 7 × 2 (multiplication) is done first

Step-by-step explanation:

from the mnemonic PEDMAS, the order of operations are: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.

hence in the first expression : 42 (17 – 15) / (3 + 1) – 5, the parenthesis (bracket is simplified first as follows:

(17 - 15) = (2) ;  and (3 + 1) = (4) ;  hence the expression will be simplified as follows: 42 (2) / (4) - 5.

Next, since there is no exponent in the expression, Multiplication follows:

42 (2) = 42 × 2 = 84 ; hence he expression becomes: 84 / 4 - 5

Next division follows : 84/4 = 21, therefore the expression becomes

21 - 5.

Finally, subtraction follows : 21 - 5 = 16

b)  5 + 7 x 2 - 9;

first, multiplication is done: 7 × 2 = 14, hence the expression becomes :

5 + 14 - 9.

Next in the order is addition : 5 + 14 = 19, hence, the expression becomes:

19 - 9.

Finally, subtraction follows: 19 - 9 = 10

step-by-step explanation: