Anonymous
Anonymous asked in Science & MathematicsMathematics · 1 decade ago

Help on Math show all work?

8. 12k + 7 = 31..i know k=2 but i just don't know how to show the work for it

9. 13n + 42 = 81..i know n= 3 but i just don't know how to show the work for it

10. 56 = 17p - 29

11. w/4 - 21 = -3

Update:

serious answers ONLY please thanks

10 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    8.

    12k = 31 - 7

    12k = 24

    k = 24 / 12

    k = 2

    9.

    13n + 42 = 81

    13n = 81 - 42

    13n = 39

    n = 39 / 13

    n = 3

    10.

    56 = 17p - 29

    56 + 29 = 17p

    85 = 17p

    p = 85 / 17

    p = 5

    11.

    w/4 - 21 = -3

    w / 4 = -3 + 21

    w / 4 = 18

    w = 18 x 4

    w = 72

    One question: how did you know the answers to 8 and 9 if you didnt know how to get to those answers?

  • 1 decade ago

    8. 12k + 7 = 31

    12k = 31 - 7

    12k = 24

    k = 2

    9. 13n + 42 = 81

    13n = 81 - 42

    13n = 39

    n = 3

    10. 56 = 17p - 29

    17p = 85

    p = 5

    11. w/4 - 21 = -3

    w - 84 = -12

    w = 72

  • Anonymous
    1 decade ago

    12k plus 7 = 31

    Minus seven to get rid of it and minus seven on the other side.

    so 31 minus 7

    Then once you have the answer. Divide 12 by 12 and the same to the 31 minus 7 answer.

    What ever you do on one side, you to do the other. Opposite of the integer sign also. So if it's 2k plus 7 you minus seven to get rid of it and minus seven on the other side.

    8. 12k + 7 = 31

    12k = 31 - 7

    12k = 24

    k = 2

    9. 13n + 42 = 81

    13n = 81 - 42

    13n = 39

    n = 3

    10. 56 = 17p - 29

    17p = 85

    p = 5

    11. w/4 - 21 = -3

    w - 84 = -12

    w = 72

    Do the same for all of them. Good Luck!

  • 1 decade ago

    Yep here you go.....hope this helps

    8. 12k + 7 = 31

    12k = 31-7

    12k = 24

    12k/12 = 24/12

    k = 2

    9. is the same way

    10. is the same as 8 and 9

    11. w/4 - 21 = -3

    w/4 = -3 + 21

    w/4 = 18

    w/4 *(4) = 18 * (4)

    w = 72

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  • 1 decade ago

    12k + 7 = 31

    -7 -7

    12k=24

    12k/12=24/12=2

    13n+42=81

    -42 -42

    13n/13=39/13= 3

    56=17p-29

    +29 +29

    85=17p

    85/17=17p/17

    =5

    and I'm not sure on the last one.

  • 1 decade ago

    place all the numbers to the right of the equal sign, if a number crosses the equal sign, change the sign and then add:

    12k + 7 = 31

    12k = 31 - 7

    12k = 24

    k = 24/12

    k = 2

    Source(s): 9th grade math
  • Anonymous
    1 decade ago

    12k+7=31

    12k=31-7

    12k=24

    k=24/12 (the '/' means divided by)

    k=2

    there ya go! your just simply swaping sides with everything.. heres another..

    sorry i dnt have enough time to do them all.. hopefully you get the idea

    13n+42=81

    13n=81-42

    13n=39

    n=39/13

    n=3

  • 1 decade ago

    12(2) + 7 = 31

    24+7=31

    31=31

    13(3) + 42 = 81

    39 + 42 = 81

    81=81

    17p - 29 = 56

    ------ ------

    17 17

    p - 29 = 3.3 Not so sure about this one...?

    +-29 +-29

    --------------------

    p = -25.7 ???

    w

    --- - 21 = -3

    4

    (4)w

    ------- -21 = -3 (4)

    w -12

    W - 21 = -12

    +-21 +-21

    ---------------------

    W = -33

    Hope i helped. good luck. :D

    Source(s): Pre- Alg. :D
  • Anonymous
    5 years ago

    42= c+(c+8) 42= 2c+8 34=2c 17=c <there's the shorter call now add 8 for the longer call 17+8=25 and to check we add 17 to 25 and get 42, the total the phone bill said we had talked

  • 1 decade ago

    are you joking me what grade are you in 5th i think you should ask your math teacher because this is just stupid!!!!!!!!!!!!!!! who goes online and asks for help in the internet

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