If 3x + 2y = 7 and 2x – y = 7, what is the value of x ? - The Beat The GMAT Forum

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pm; Location: Vancouver, BC; Thanked: 5254 times; Followed by:1268 members; GMAT Score:770

Re: If 3x + 2y = 7 and 2x – y = 7, what is the value of x ?

by Brent@GMATPrepNow » Thu Apr 08, 2021 6:18 am

BTGmoderatorDC wrote: ↑
Mon Apr 05, 2021 7:27 pm
If 3x + 2y = 7 and 2x – y = 7, what is the value of x ?

A. 0
B. 1
C. 7/5
D. 21/11
E. 3

OA E

Source: GMAT Prep

Let's use the elimination method to solve this system

Given:
3x + 2y = 7
2x – y = 7

Multiply both sides of the bottom equation by 2 to get the following equivalent equation:
3x + 2y = 7
4x – 2y = 14

Now add the two equations to get:
7x = 21

Solve: x = 3

Answer: E

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8085; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

Re: If 3x + 2y = 7 and 2x – y = 7, what is the value of x ?

by Scott@TargetTestPrep » Fri Apr 16, 2021 8:13 am

BTGmoderatorDC wrote: ↑
Mon Apr 05, 2021 7:27 pm
If 3x + 2y = 7 and 2x – y = 7, what is the value of x ?

A. 0
B. 1
C. 7/5
D. 21/11
E. 3

OA E

Source: GMAT Prep

Solution:

If we subtract the second equation from the first, we have:

x + 3y = 0

3y = -x

y = -x/3

Substituting this in the first equation, we have:

3x + 2(-x/3) = 7

9x - 2x = 21

7x = 21

x = 3

Answer: E

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