Blake has only nickels and dimes.
He has twice as many nickels as dimes. The total value of his coins is 60¢. What coins does Blake have?
_____ nickels _____ dimes
n = 2d
5n + 10d = 60
solving that, you get
5(2d) + 10d = 60
20d = 60
d = 3
so there are 3 dimes and 2*3 = 6 nickels