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Kirby
Lv 7
Kirby asked in Science & MathematicsMathematics · 1 decade ago

Am I doing this right? (solving a system using substitution method)?

I'm pretty sure I did something wrong but I don't know what...

x-7y=12

2x+8y=14

-2x

8y=14-2x

x-7(14-2x)=12

x-98-14x=12

+98 +98

13x=110

110/13=8.5

x=8.5???

is that right?

Update:

so it's negative 8.5 then?!

Update 2:

um 2nd answer...how did you get divided by 8?

Update 3:

oh nvm....

4 Answers

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  • 1 decade ago
    Favorite Answer

    Why do this the hard way?

    x = 7y + 12

    2(7y + 12) + 8y = 14

    14y + 24 + 8y = 14

    22y = -10

    y = -5/11

    x - 7y = 12

    x - 7(-5/11) = 12

    x + 35/11 = 12

    11x + 35 = 132

    11x = 97

    x = 97/11

    Here's where you made your mistake. You show that 8y = 14 - 2x, but then you substitute that for y in the equation. y = (14 - 2x)/8, and that is what you should substitute.

    But since you already have a unit variable (x) in the first equation, use that.

  • 4 years ago

    you prefer to unravel for between the unknowns in the least confusing equation. utilising p + q = 4, you are able to resolve for q and get q = 4 - p. by using substitution, enter 4 - p in for q in the different equation: 4p + q = a million 4p + 4 - p = a million 3p + 4 = a million 3p = -3 p = -a million Now you have solved for p. you are able to now resolve for q by using putting your fee for p back into between the equations. I"m going to compliment the main elementary one: p + q = 4 -a million + q = 4 q = 5.

  • 1 decade ago

    You said that 8y=14-2x but then contradicted yourself, because you said x-7(14-2x)=12. here, you said that y=14-2x

    then, when you distributed, you said -7 * -2x is -14x, but it is +14x, cuz a negative and a negative is a positive,

    after, you said x-14x is 13x but it is -13x.

  • Anonymous
    1 decade ago

    the person under me said u did wrong?do u want to correct it?

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