SOLUTION: I don't know where to start. Can you explain what I am meant to be doing to solve these two questions? a) 3x + 2y = 5 y = 5x - 17 b) 2x + 3y = 21 x

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Question 71929: I don't know where to start. Can you explain what I am meant to be doing to solve these two questions?
a) 3x + 2y = 5
y = 5x - 17
b) 2x + 3y = 21
x - y = 18
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
a) 3x + 2y = 5
y = 5x - 17
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Substitute y=5x-1 into the 1st equation in order to solve for "x":
3x + 2(5x-17) = 5
3x + 10x-34 = 5
13x=39
x=3
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Substitute that value of x into y=5x-17 to solve for "y":
y=5*3-17
y=-2
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Solution x=3 and y=-2
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b) 2x + 3y = 21
x - y = 18
Solve for y: y=x-18
Substitute in the 1st equation to solve for "x":
2x+3(x-18)=21
2x+3x-54=21
5x=75
x=15
Substitute that into y=x-18 to solve for "y":
y=15-18
y=-3
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Solution: x=15; y=-3
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Cheers,
Stan H.

SOLUTION: I don't know where to start. Can you explain what I am meant to be doing to solve these two questions? a) 3x + 2y = 5 y = 5x - 17 b) 2x + 3y = 21 x - y = 18