Anna has 16 nickels
Solution:
Let "n" be the number of nickels
Let "q" be the number of quarters
We know that,
1 nickel = $ 0.05 or 5 cent
1 quarter = $ 0.25 or 25 cent
Anna has a collection of 45 nickels and quarters
Therefore,
n + q = 45
q = 45 - n --------- eqn 1
Anna has a collection of 45 nickels and quarters worth $8.05
$ 8.05 is worth 805 cents
Thus we frame a equation as:
number of nickels x 5 cents + number of quarters x 25 cents = 805
5n + 25q = 805 ----- eqn 2
Let us solve eqn 1 and eqn 2
Substitute eqn 1 in eqn 2
5n + 25(45 - n) = 805
5n + 1125 - 25n = 805
20n = 1125 - 805
20n = 320
n = 16
Thus Anna has 16 nickels