Question 983086
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5x+y=9
y=9-5x Use this to substitute for y.
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10x-7y=-18 Substitute for y from above.
10x-7(9-5x)=-18
10x-63+35x=-18
45x=45
x=1 
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y=9-5x=9-5=4
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ANSWER: x=1 and y=4
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CHECK:
5x+y=9
5(1)+4=9
9=9
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10x-7y=-18
10(1)-7(4)=-18
10-28=-18
-18=-18