SOLUTION: The sum of three numbers is forty-two. The second number is twice the first number and the third number is three less than the second number. Find the three numbers

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Question 837343: The sum of three numbers is forty-two. The second number is twice the first number and the third number is three less than the second number. Find the three numbers
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
x, y, and z are the numbers.
x%2By%2Bz=42
y=2x, and z=y-3
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Any route you see or find, try.
One I see is z=42-x-y from first equation.
z=y-3=42-x-y, to equate expressions for z.
2y%2Bx=42%2B3
x%2B2y=45----- which only uses x and y.
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One of the equations from the description also uses only x and y, so we have this simple system of two variables:
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y=2x
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x+2y=45
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A simple substitution will be best next step.
x%2B2%2A2x=45
5x=45
highlight%28x=9%29-------You have one variable's value solved.
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Also created y=2x from the description, so
y=2%2A9=highlight%2818=y%29 ----- another variable found.
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Given from description
z=y-3
z=18-3
highlight%28z=15%29------the last variable found.