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If 4x−3y=10 and 7x−8y=34 , what is the value x−y ?

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If 4x−3y=10 and 7x−8y=34 , what is the value x−y ?  [#permalink]

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New post 01 Mar 2017, 05:41
2
3
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

80% (01:54) correct 20% (02:15) wrong based on 144 sessions

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Re: If 4x−3y=10 and 7x−8y=34 , what is the value x−y ?  [#permalink]

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New post 01 Mar 2017, 05:50
2
Top Contributor
2
Bunuel wrote:
If 4x−3y=10 and 7x−8y=34, what is the value x−y?

A. 2
B. 4
C. 6
D. 8
E. 12


Nice question!

The long approach is to solve the system for the INDIVIDUAL values of x and y and then use those values to determine the value of x-y.

The quick approach is to ADD the two equations (4x−3y=10 and 7x−8y=34) to get: 11x - 11y = 44
Then divide both sides by 11 to get: x - y = 4

Answer: B

Cheers,
Brent
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Re: If 4x−3y=10 and 7x−8y=34 , what is the value x−y ?  [#permalink]

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New post 01 Mar 2017, 11:44
Bunuel wrote:
If 4x−3y=10 and 7x−8y=34, what is the value x−y?

A. 2
B. 4
C. 6
D. 8
E. 12


\(4x − 3y = 10 ---------------> (I)\)
\(7x − 8y = 34 ---------------> (II)\)

Add (I) and (II)

\(11x − 11y = 44\)

Or, \(x − y = 4\)

Thus, answer must be (B) 4
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Re: If 4x−3y=10 and 7x−8y=34 , what is the value x−y ?  [#permalink]

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New post 02 Mar 2017, 18:40
1
Bunuel wrote:
If 4x−3y=10 and 7x−8y=34, what is the value x−y?

A. 2
B. 4
C. 6
D. 8
E. 12


Adding the two equations together, we have:

4x - 3y = 10

7x - 8y = 34

11x - 11y = 44

Dividing both sides by 11, we have:

x - y = 4

Answer: B
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Re: If 4x−3y=10 and 7x−8y=34 , what is the value x−y ?  [#permalink]

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New post 02 Apr 2018, 22:46
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: If 4x−3y=10 and 7x−8y=34 , what is the value x−y ? &nbs [#permalink] 02 Apr 2018, 22:46
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