You have a total of 21 coins, all nickels and dimes. The total value is $1.70. Write and solve a system of equations to find the number of dimes d and the number of nickels n that you have.

To solve this problem you must apply the following proccedure:

1. You have a total of 21 coins, all nickels and dimes. Then:

x:nickels=5 cents

y: dimes=10 cents

x+y=21

2. You have that the total value is $1.70. Then:

5x+10y=170

3. The system of equation is:

x+y=21 (i)

5x+10y=170 (ii)

4. You have:

x+y=21

x=21-y

5 (21-y) + 10y=170

105-5y+10y=170

y=13 dimes

x+13=21

x=8 nickels