Question 366683
 Joe has a collection of nickels and dimes that is worth $6.20. If the number of dimes was doubled and nickels were decreased by 37, the value of the coins would be worth $4.20. How many nickels and dimes does Joe have? 
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n = # of nickels
d = # of dimes
5n + 10d = 620
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5(n-37) + 20d = 420
5n-185 + 20d = 420
5n + 20d = 605
5n + 10d = 620
--------------- Subtract
20d = -15
No meaningful solution.