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Question 186715: can you please help me with the math problem i got stuck on.
my teacher says we need the bottom equation to solve the top equation then to find the answer to the bottom equation after.
0.3x-0.2y=0.5
x-2y=-5
Answer by nerdybill(7384)   (Show Source):
You can put this solution on YOUR website! my teacher says we need the bottom equation to solve the top equation then to find the answer to the bottom equation after.
0.3x-0.2y = 0.5 (top equation)
x- 2y = -5 (bottom equation)
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Taking the "bottom equation", let's solve for 'x':
x- 2y = -5
adding 2y to both sides we get:
x = 2y -5
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Now, we take the above, and substitute it into the "top equation":
0.3x-0.2y = 0.5
0.3(2y -5)-0.2y = 0.5
distributing the 0.3 to terms inside the parenthesis:
0.6y-1.5 -0.2y = 0.5
combining y's:
0.4y-1.5 = 0.5
adding 1.5 to both sides:
0.4y = 2
y = 2/0.4
y = 5 (solution for y)
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Finally, we take the above solution of y and plug it back into the bottom equation and solve for x:
x- 2y = -5
x- 2(5) = -5
x- 10 = -5
adding 10 to both sides:
x = 5 (solution for x)
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Solution:
y=5
x=5
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The above method is called the "substitution method".
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