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Math Help - solvind simple equations

  1. #1
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    solvind simple equations

    -r + 18 = -39 ... -r +18-18 = -39 + -18 = -r + 0 = -57. my study gude says the answer is 57 can someone please help me understand how the answer could be 57. and not -57
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  2. #2
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    Quote Originally Posted by Leona_Marie View Post
    -r + 18 = -39 ... -r +18-18 = -39 + -18 = -r + 0 = -57. my study gude says the answer is 57 can someone please help me understand how the answer could be 57. and not -57

    -r=-57 , note that there are negative signs at both sides , cancelling both the signs , you should get r=57 .
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    Quote Originally Posted by mathaddict View Post
    -r=-57 , note that there are negative signs at both sides , cancelling both the signs , you should get r=57 .
    but 57 + 18 doesnt = -39 please explain
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  4. #4
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    Quote Originally Posted by Leona_Marie View Post
    but 57 + 18 doesnt = -39 please explain

    Alright , lets start from the begining again.

    -r + 18 = -39
    -r +18 -18 =-39-18

    -r=-57

    r=57

    How did u come to this , 57 + 18 doesnt = -39 ??
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  5. #5
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    .(how do i delete this mmessage didnt mean to post it?
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  6. #6
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    Quote Originally Posted by mathaddict View Post
    Alright , lets start from the begining again.

    -r + 18 = -39
    -r +18 -18 =-39-18

    -r=-57

    r=57

    How did u come to this , 57 + 18 doesnt = -39 ??
    yes I am new to this I figure -r + 18 should equal -39
    if the answer is 57, well 57+18 is 75 but-57 +18 = -39 Im confused
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  7. #7
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    Quote Originally Posted by Leona_Marie View Post
    yes I am new to this I figure -r + 18 should equal -39
    if the answer is 57, well 57+18 is 75 but-57 +18 = -39 Im confused
    Hi Leona,

    It's very simple. Watch

    -r+18=-39

    First we subtract 18 from both sides giving us:

    -r+18-18=-39-18

    -r=-57

    But, we're not done. We must find a solution for r, not -r. To find r, we multiply both sides of the equation by -1.

    (-1)(-r)=(-1)(-57)

    \boxed{r=57}

    To check this we start with our original equation:

    -r+18=-39

    Substitute 57 in for r to get:

    -(57)+18=-39

    Notice, the negative sign was already part of the equation. I just replaced r with 57. Now the check is fine.

    -57+18=39
    -39=-39
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  8. #8
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    this is the second time you helped me to understand Id like to thank you but still I dont know where the thank but is exactly.
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