Question 575229
Mrs.Boyd has a desk full of quarters and nickels. If she has a total of 16 coins with a total face value of 3.00$, how many of the coins were nickels?
sol:
Then 0.25x is the dollar amount of one quarter (1x) and 0.05 is the dollar amount of one nickel (1y). 
x + y = 16 (the number of quarters and nickels if you count them as coins)
0.25x + 0.05y = $3 (the amount of money if you add the value of all the quarters and nickels. 
solving this for x & y you get the no of quaters and nickels respectively.