The value of 25 coins, consisting of dimes and quarters, is $ 3.55. How many dimes are in the collection?
Let x = # of dimes and y = # of quarters
x + y = 25
y = 25-x
10x + 25y = 355
Substitute 25-x for y in last equation and solve for x.
x + y = 25
y = 25-x
10x + 25y = 355
Substitute 25-x for y in last equation and solve for x.