Question 500701
x = first number
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y = second number is 6 less than x
y = x-6
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z = third number is 2 x
z = 2*x
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x + y + z = 306
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Substitute
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x + (x-6) + 2x = 306
4x = 312
x = 78
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y = 78 -6
y = 72
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z = 2x
z = 2*78
z = 156
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Always check your work.
78+72+156 = ??
 = 306
Correct.
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Answer:  The three numbers are  78, 72, and 156.
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Done.