Question 158960
    Amber has 30 coins in nickles and dimes. In all she has $2.10. How many nickles and dimes does she have. 
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Let n = number of nickels
then, because there is a total of 30 coins
30-n = number of dimes
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Because, we know the total is $2.10
"amt from nickels" + "amt from dimes" = $2.10
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.05n + .10(30-n) = 2.10
.05n + 3 - .10n = 2.10
3 - .05n = 2.10
3 = .05n+2.10
.90 = .05n
.90/.05 = n
18 = n (number of nickels)
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number of dimes:
30-n = 30-18 = 12 (number of dimes)