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Moderator  Joined: 18 Apr 2015
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If x and y satisfy the system of equat [#permalink]
Expert's post 00:00

Question Stats: 33% (02:24) correct 66% (02:36) wrong based on 3 sessions
$$7x + 3y = 12$$
$$3x + 7y = 6$$

If x and y satisfy the system of equations above, what is the value of x - y?

A. $$\frac{2}{3}$$

B. $$\frac{3}{2}$$

C. $$1$$

D. $$4$$

E. $$6$$

Kudos for the right answer and explanation
[Reveal] Spoiler: OA

_________________ Manager  Joined: 15 Jan 2018
Posts: 147
GMAT 1: Q V
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Re: If x and y satisfy the system of equat [#permalink]
1
KUDOS
If you're not getting the answer choices to this restaurant, I'm not surprised. They aren't there. This problem needs to be retyped. Let's try anyway.

In order to solve for x, let's multiply the above equation by 7 and the below equation by 3. This will produce a 21y in both equations, which can then be easily subtracted out.

7x + 3y = 12
3x + 7y = 6

becomes

49x + 21y = 84
9x + 21y = 18

Subtracting we get

40x = 66
so
x = 66/40 = 33/20

Plugging that into one of the equations we will get 3/20 for y.
33/20 x
3/20 y
_________________

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Need help with GRE math? Check out our ground-breaking books and app. Re: If x and y satisfy the system of equat   [#permalink] 06 Mar 2018, 16:15
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