Question 1008625
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N=nickels; D=dimes
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N+D=20
D=20-N
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$0.05N+$0.10D=$0.10N+$0.05D-$0.30
$0.05D=$0.05N-$0.30
$0.05(20-N)=$0.05N-$0.30
$1.00-$0.05N=$0.05N-$0.30
$1.30=$0.10N
13=N
ANSWER 1: He has 13 nickels.
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D=20-N=20-13=7
ANSWER 2: He had 7 dimes.
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CHECK:
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$0.05N+$0.10D=$0.10N+$0.05D-$0.30
$0.05(13)+$0.10(7)=$0.10(13)+$0.05(7)-$0.30
$0.65+$0.70=$1.30+$0.35-$0.30
$1.35=$1.35