We first have to write an expression for each of the types of coins in terms of one of them. If he has 8 more dimes than nickels, let's call nickels "x". That means that dimes is "x + 8". The value of a nickel is .05, so the expression relating the number of nickels to the worth of the nickel is .05x. The value of a dime is .10, so the expression relating the number of dimes to the worth of the dime is .10(x + 8). The total value of these coins is 1.70:
