Algebra
posted by Jon .
Mrs. Boyd has a desk full of quarters and nickels. If she has a total of 31 coins with a total face value of $4.55, how many of the coins are nickels?

q = # of quarters
n = # of nickels
q + n = 31 coins
Now, you need the value of the coins:
.25q + .05n =4.55
I would multiply by 100 to get rid of the decimals
25q + 5n = 455
q + n + 31
(multiply this equation by negative 5 and add.)
You will solve for quarters and then you can find nickels