System of equations, solving for two unknown variables. : GMAT Quantitative Section
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# System of equations, solving for two unknown variables.

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Intern
Joined: 11 Aug 2013
Posts: 34
Followers: 0

Kudos [?]: 9 [0], given: 9

System of equations, solving for two unknown variables. [#permalink]

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15 Aug 2013, 14:21
Kudos to detailed explained answers. Please pick one and solve. Please choose if you'll be using substitution or combination.

31. X-Y=4
2x+Y=5

33. A+B=8
2A+B=13

35. Y-2x-1=0
X-3y-1=0

37. 5x+2y=12
Y=1/2x+3
Manager
Joined: 21 Aug 2012
Posts: 150
Followers: 2

Kudos [?]: 60 [1] , given: 41

Re: System of equations, solving for two unknown variables. [#permalink]

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15 Aug 2013, 18:55
1
KUDOS
selfishmofo wrote:
Kudos to detailed explained answers. Please pick one and solve. Please choose if you'll be using substitution or combination.

31. X-Y=4
2x+Y=5

33. A+B=8
2A+B=13

35. Y-2x-1=0
X-3y-1=0

37. 5x+2y=12
Y=1/2x+3

Hi,

31. X-Y=4 -----a
2x+Y=5 ----b

Now, 2X-2Y = 8 for a
2X+Y=5

Subtracting these two equations,
3Y = -3
Y= -1
Hence, X = 4+Y =4-1 => 3

33. A+B=8 ----c
2A+B=13 -----d

d - c => A =5, Hence B=8-A=> 3

35. Y-2x-1=0 ----e
X-3y-1=0 ---- f

Multiply equation f by 2 and adding with e

2X - 6Y -2 =0
-2X + Y -1 =0
---------------------------
-5Y - 3 =0
Hence, Y= -3/5
Putting values of Y either in e or f, we get X= -4/5

37. 5x+2y=12
Y=1/2x+3

Please clarify whether it is 1/(2x) + 3 or 1 / (2x+3).
_________________

MODULUS Concept ---> http://gmatclub.com/forum/inequalities-158054.html#p1257636
HEXAGON Theory ---> http://gmatclub.com/forum/hexagon-theory-tips-to-solve-any-heaxgon-question-158189.html#p1258308

Intern
Joined: 11 Aug 2013
Posts: 34
Followers: 0

Kudos [?]: 9 [0], given: 9

Re: System of equations, solving for two unknown variables. [#permalink]

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16 Aug 2013, 18:38
I'm not sure now, the other problems work. Thank you for solving them.
Manager
Joined: 21 Aug 2012
Posts: 150
Followers: 2

Kudos [?]: 60 [1] , given: 41

Re: System of equations, solving for two unknown variables. [#permalink]

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16 Aug 2013, 20:01
1
KUDOS
selfishmofo wrote:
I'm not sure now, the other problems work. Thank you for solving them.

We all are here to help each other..!!!

Thanks,
Jai
_________________

MODULUS Concept ---> http://gmatclub.com/forum/inequalities-158054.html#p1257636
HEXAGON Theory ---> http://gmatclub.com/forum/hexagon-theory-tips-to-solve-any-heaxgon-question-158189.html#p1258308

Re: System of equations, solving for two unknown variables.   [#permalink] 16 Aug 2013, 20:01
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