SOLUTION: how do you solve 5x-7y=9,4x-3y=33

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Question 407761: how do you solve 5x-7y=9,4x-3y=33
Found 2 solutions by Tatiana_Stebko, mananth:
Answer by Tatiana_Stebko(1539) About Me  (Show Source):
You can put this solution on YOUR website!
system%285x-7y=9%2C4x-3y=33%29
Multiply the first equation by 3, the second equation by (-7)
system%2815x-21y=27%2C-28x%2B21y=-231%29
In this way we have the same coefficient, but with different sign, in front of y. If after that we add the first equation to the second equation, the second equation will have only x.
system%2815x-21y=27%2C-28x%2B15x=-231%2B27%29, system%2815x-21y=27%2C-13x=-204%29, system%2815x-21y=27%2Cx=204%2F13%29
Put x=204%2F13 in the first equation
system%28x=204%2F13%2C+15%2A%28204%2F13%29-21y=27%29, system%28x=204%2F13%2C+y=129%2F13%29
x=159%2F13
y=912%2F13

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
5x-7y=9 .............1
4x-3y=33.............2

multiply (1)by -4
Multiply (2) by 5
-20x+28y=-36
20x-15y=165

Add the two equations

13y=129
/13

y=9.92
Plug value of y in
5x-7y=9
5x-69.46 = 9
5x=78.46
/5
x=15.69