Question 429582
Use Linear Combinations to solve the Linear System

2-7x=9y
2y-4x=6 
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Not sure what you mean by combinations.  I'll use elimination, which in a way combines the 2 eqns.
2-7x=9y
2y-4x=6 
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9y+7x = 2 eqn 1
1y-2x = 3 eqn 2 divided by 2
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9y + 7x = 2 eqn 1
9y -18x = 27 eqn 2 divided by 2 then x9
---------- Subtract
0y +25x = -25
x = -1
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1y-2x = 3  Sub for x
y + 2 = 3
y = 1
That's it.