Question 143289
Joe has a collection of nickels and dimes that is worth $5.65.
5n + 10d = 565 cents
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If the number of dimes were doubled and the number of nickels were increased by 8, the value of the coins would be $10.45. 
5(n+8) + 10(2d) = 1045 cents
5n+40 + 20d = 1045
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How many dimes does he have? 
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EQUATIONS:
5n   +   10d  = 565
5n   +   20d  = 1005
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10d = 440
d = 44 (# of dimes)
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Substitute into 5n+10d = 565 to solve for "n":
5n +440 = 565
5n = 125
n = 25 (# of nickels)
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Cheers,
Stan H.