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If 4x−3y=10 and 7x−8y=34, what is the value x−y? A. 2 B. 4 C. 6 D. 8
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03 Mar 2021, 02:27
03 Mar 2021, 02:27
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If 4x−3y=10 and 7x−8y=34, what is the value x−y?
A. 2
B. 4
C. 6
D. 8
E. 12
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
A. 2
B. 4
C. 6
D. 8
E. 12
Kudos for the right answer and explanation
Question part of the project GRE Quantitative Reasoning Daily Challenge - (2021) EDITION
GRE - Math Book
Retired Moderator
Joined: 16 Apr 2020
Status:Founder & Quant Trainer
Affiliations: Prepster Education
Posts: 1546
Given Kudos: 172
Location: India
WE:Education (Education)
Re: If 4x−3y=10 and 7x−8y=34, what is the value x−y? A. 2 B. 4 C. 6 D. 8
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03 Mar 2021, 04:07
03 Mar 2021, 04:07
1
Carcass 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
A. 2
B. 4
C. 6
D. 8
E. 12
4x − 3y = 10 ........ (1)
7x − 8y = 34 ........ (2)
Multiplying (1) by 7 and (2) by 4;
28x - 21y = 70
28x - 32y = 136
11y = -66
y = -6
So, 4x - 3(-6) = 10
x = -2
Now, x - y = -2 - (-6) = 4
Hence, option B
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
Re: If 4x−3y=10 and 7x−8y=34, what is the value x−y? A. 2 B. 4 C. 6 D. 8
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03 Mar 2021, 07:29
03 Mar 2021, 07:29
2
Carcass 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
A. 2
B. 4
C. 6
D. 8
E. 12
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
