SOLUTION: Tabitha has $3.20 in quarters and nickels. If she has 20 coins in all, how many quarters does she have?

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Question 370210: Tabitha has $3.20 in quarters and nickels. If she has 20 coins in all, how many quarters does she have?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let Q be the number of quarters, D dimes.
1.Q%2BD=20
.
.
25Q%2B10D=320
2.5Q%2B2D=64
Multiply eq. 1 by -2 and add to eq. 2,
-2Q-2D%2B5Q%2B2D=-40%2B64
3Q=24
highlight%28Q=8%29
Then from eq. 1,
8%2BD=20
highlight%28D=12%29