Question 281309
Trying to help my duaghter with the folowing problem. 
one side will be 5x+y = 7 
the other side is 3x-4y=18 We need to solve for x and y.
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5x+y = 7
3x-4y = 18
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Two popular methods for solvin "systems" of equations
are substitution and elimination.
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I'll show you both ways since your daughter may not have
been introduced to one or the other.
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Substitution:
5x+y = 7
3x-4y = 18
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Solve the 1st equation for "y":
y = -5x+7
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Substitute for "y" in the 2nd equation:
3x - 4(-5x+7) = 18
3x + 20x - 28 = 18
23x - 28 = 18
23x = 46
x = 2
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Subtitute for x in the equation y = -5x+7
y = -5(2)+7
y = -10+7
y = -3
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Final Answer: (2,-3)
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Elimination:
5x+y = 7
3x-4y = 18
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Multiply both sides of the 1st equation by 4 to get:
20x + 4y = 28
3x - 4y = 18
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Add to get:
23x = 46
x = 2
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Substitute that value of "x" into either of the 
original equations and solve for "y":
5x+y = 7
5*2+y = 7
10+y = 7
y = -3
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Final Answer: (2,-3)
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Cheers,
Stan H.