1 nickle = 5 cents

1 dime = 10 cents

$1.70 = 170 cents

let

n = the number of nickles, n>=0

d = the number of dimes, d>=0

A coin collector has $1.70 in dimes and nickels:

10d + 5n = 170

She has two more dimes than nickels:

d = n + 2

by solving the system of equations:

10d + 5n = 170

d = n + 2

we find:

d = 12 dimes

n = 10 nickles

click here to see the step by step solution of the system of equations:

She has 10 nickles.