Question 105688
Let x = nickles
Let y = dimes
.
.05x + .10y = 1.00
x+y=15
y=15-x
So, 
.05x + .10(15-x)=1.00
.05x + 1.5 - .10x = 1.00
-.05x + 1.5 = 1.00
-.05x = 1.00 - 1.5
-.05x = -.50
-.05x/-.05 = -.50/-.05
x=10
x+y=15
10+y=15
y=15-10
y=5
.
Checking: 
0.05(10) + .10(5)=1.00
.50 +.50=1.00
1.00=1.00 (checks out)