You have a total of 21 coins, all nickles and dimes. The total value is $1.70 Which of the following is the system of linear equations that represent this scenario? Let n = the number of nickles and let d = the number of dimes.

You need one equation for the physical nickels and dimes, which total to 21:

n+d=21

Secondly, you need one equation for the numerical value of those nickels and dimes. We know nickels are worth $0.05 and dime are worth $0.10:

.05n+.1d=1.70