First, let's call the number of dimes Jocelyn has dd and the number of nickels she has nn. We then know the number of dimes and the number of nickels are 27 or d + n = 27d+n=27
We can solve this for dd:
d + n - n = 27 - nd+n−n=27−n
d = 27 - nd=27−n
Next we know a dime is worth $0.10$0.10 and a nickel is worth $0.05$0.05 and we know she has a total of $1.95$1.95 in her pocket so we can write:
$0.10d + $0.05n = $1.95$0.10d+$0.05n=$1.95
From the first equation we can substitute 27 - n27−n for dd in the second equation and solve for nn;
$0.10(27 - n) + $0.05n = $1.95$0.10(27−n)+$0.05n=$1.95
($0.10*27) - $0.10n + $0.05n = $1.95($0.10⋅27)−$0.10n+$0.05n=$1.95
$2.70 - $0.05n = $1.95$2.70−$0.05n=$1.95
$2.70 - $2.70 - $0.05n = $1.95 - $2.70$2.70−$2.70−$0.05n=$1.95−$2.70
-$0.05n = -$0.75−$0.05n=−$0.75
(-$0.05n)/(-$0.05) = (-$0.75)/(-$0.05)−$0.05n−$0.05=−$0.75−$0.05
n = 15n=15
Now that we know there are 15 nickels (n = 15n=15) we can substitute 1515 for nn in the solution for the first equation and calculate the number of dimes or dd:
d = 27 - 15d=27−15
d = 12d=12