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Solve for x in the two equations using substitution. I can't figure this out!?

0 votes

Solve for x in the two equations below using substitution 

9x + 3y = 6 
2x + 3y = 7 

A. x= -1/7 
B. x= 13/7 
C. x= 13/11 
D. x= 1/7 

I have spent a long time on this one question. This is on study island and I can't miss this question or else I fail the test. Please help me out! If you can, explain how you solve it please!

asked Feb 11, 2014 in PRE-ALGEBRA by anonymous Apprentice

1 Answer

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Given equations are 9x+3y = 6 ---> (1)

2x+3y = 7

Subtract 2x from each side.

2x-2x+3y = 7-2x

3y = 7-2x

Divide to each side by 3.

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

y = (7-2x)/3 ---> (2)

Substitute the y value from (2) in (1).

9x+3(7-2x)/3 = 6

9x+7-2x = 6

7x+7 = 6

Subtract 7 from each side.

7x+7-7 = 6-7

7x = -1

Divide  to each sideby 7.

7x/7 = -1/7

x = -1/7

Option A is correct choice.

 

answered Feb 11, 2014 by ashokavf Scholar

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