Question

Simplify the expression twenty-one minus seven times two plus nine. Show your work. Then, show how the solution is affected if addition and subtraction are not applied from left to right.

Answer 1

Can someone please help me i've been on this problem forever and i cant seem to figure it out someone please help!?

Answer 2

so do you mean 21-7x2+9?

Answer 3

yes

Answer 4

oh ok so did you solve it already and just need help with the second question?

Answer 5

no sadly i need help with everything i did not even start i cant seem to understand it :(

Answer 6

no it's fine! :) do you know PEMDAS? or have you heard of it?

Answer 7

yes i do know what pemdas means please excuse my dear ant sally

Answer 8

yes! :) do you know how to use it when you solve a problem?

Answer 9

yes on some problems not all :o

Answer 10

ok that's fine. so i would first multiply 7x2 then subtract 21 then add 9. The reason why i did not add then subtract which i would usually do, is because the second question says "Then, show how the solution is affected if addition and subtraction are not applied from left to right." so i have to do it exactly from left to right. Then i would do it right to left..... did i confuse you at all?

Answer 11

Nope not at all im understanding :D

Answer 12

oh ok! Great i was so worried i was confusing you not helping you! :) so can you tell me, if you solve the problem from left to right what the answer will be?

Answer 13

the answer will be 2

Answer 14

how did you get 2?

Answer 15

i did how pemdas tells me how to do it i multiplyed then i suptarcted then i added

Answer 16

that's what i did and i got

21-14+9
7+9
16

Answer 17

hmm i must off put something in wrong lets try it again and lets see what i get

Answer 18

ok that's fine just take your time :)

Answer 19

yeah i did put something wrong now that ive done the whole process i got 16 :D

Answer 20

awesome! :) now what you just did was solve the problem from left to right which is right. now you do it from right to left and see if there is a difference.

Answer 21

by doing that you will be able to answer the second question

Answer 22

ok so basically the first part is answering the first part of the question and once i do the second part that will be the the answer to the second part of the question?

Answer 23

yup exactly! because once you multiply 7x2 then you add 9 then subtract 21 from your answer... you will see why you can answer question 2.

Answer 24

okay :o be right back ill be back like in 5 mins

Answer 25

that's fine

Answer 26

ok im back my answer for part 2 was 2

Answer 27

i got -2...

this is what i did:

21-7x2+9
21-14+9
21-23
-2

Answer 28

7x2=14 +9 -21

Answer 29

thats what i did

Answer 30

it's 21-23 not 23-21

Answer 31

by changing the positioning of the numbers you can change the answer

Answer 32

lol yeah my teacher said that when your subtracting you need to be careful because if you mix the numbers up it can change your whole answer

Answer 33

yeah it's fine it can get confusing in math! :D lol

Answer 34

haha so is that it theres nothing else to do right?

Answer 35

yeah! so you can answer the second question because you know that by changing the order of how you solve the problem then you are essentially changing your answer as well! :D That's all there is to it! :)

Answer 36

haha omg THANKS DO MUCH you've made my day thanks for helping me understand this :D!!

Answer 37

no it is absolutely fine i'm just glad i actually helped you and didn't confuse you! :D you made my day as well! :) lol

Answer 38

haha :)

Answer 39

:) XD

Answer 40

hey got to go thanks for help me!!! hope we can talk some other time :D

Answer 41

yah totally i would really love that! :D just send me a text or something whenever you see me I usually try to be on openstudy every 2 days or so often! :)

Answer 42

bye! :D

Answer 43

21-7+2=16(from left to right). 21-7+2=12(not from left to right) The answer decreased if you don't do it from left to right.