Question 147568
Tom and David have 480 marbles between them. Tom arranges them in columns with 6 in each column, and David arranges them with 9 in each column. The total number of columns is 72. Express the above information in the form of an algebraic equation. 

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Let David have "x" marbles:
Number of columns he has is x/6
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Let Tom have "y" marbles:
Number of columns he has is y/9
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EQUATIONS:
x + y = 480
x/6 + y/9 = 72
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Rearrange:
3x + 2y = 18*72
3x + 3y = 3*480
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y = 144 (# of marbles Tom has)
x + 144 = 480
x = 336 (# of marbles David has)
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Cheers,
Stan H.