Let the number of nickles be x and the number of dimes be y, so that means
0.05x + 0.1y=1.6
5x+10y=160...1
x=y+11...2
Put 2 into 1 that would give you
5(y+11)+10y=160
5y+55+10y=160
15y=160-55=105
y=105/15=7
x=7+11=18
So she has 18 nickels and 7 dimes