Fiona has fifty nickels and dimes whose total value is $3.40. How many of each kind of coin does she have?

n = nickels                    value = .05 n

d = dimes = (50-n)        value = .10 (50-n)        values summed = 3.40

 

.05n   +  .1 (50-n) = 3.4      solve for 'n' the number of nickels, then dimes = 50-n