$0.05(n) + $0.10(d) = $1.90
n + d = 27
n + d - d =27 - d
n = 27 - d
$0.05(27-d) + $0.10(d) = $1.90
1.35 - 0.05d + 0.10d = $1.90
1.35 +0.05d = $1.90
1.35 - 1.35 +0.05d = $1.90 -1.35
0.05d = 0.55
0.05d/0.05 = 0.55/0.05
d = 11
n = 27 - 11
n = 16
$0.05(16) + $0.10(11) = $1.90
$0.80 + $1.10 = $1.90
$1.90 = $1.90
