Question 988810
.
N=nickels; P=pennies=0.5N; D=dimes=N-39; Q=Quarters=P+N=0.5N+N=1.5N
.
$0.01P+$0.05N+$0.10D+$0.25Q=$390.42  
$0.01(0.5N)+$0.05N+$0.10(N-39)+$0.25(1.5N)=$390.42
$0.005N+$0.05N+$0.10N-$3.90+$0.375N=$390.42
$0.53N=$394.32
N=744 ANSWER 1: There were 744 nickels.
P=0.5N=0.5(744)=372 ANSWER 2: There were 372 pennies.
D=N-39=744-39=705 ANSWER 3: There were 705 dimes.
Q=1.5N=1.5(744)=1116 ANSWER 4: There were 1116 quarters.
.
CHECK:
$0.01P+$0.05N+$0.10D+$0.25Q=$390.42  
$0.01(372)+$0.05(744)+$0.10(705)+$0.25(1116)=$390.42
$3.72+$37.20+$70.50 +$279.00=$390.42
$390.42=$390.42