SOLUTION: How to set up an equation? Johnny has some dimes and quarters. He has 7 more quarters than he has dimes. If Jonny has 15 coins in all, what is the value of his coins?

Question 830989: How to set up an equation? Johnny has some dimes and quarters. He has 7 more quarters than he has dimes. If Jonny has 15 coins in all, what is the value of his coins?
Answer by JulietG(1812) (Show Source): You can put this solution on YOUR website!
Let D = dimes
Let Q = quarters
We're told the following:
D + Q = 15
Q = D + 7 (7 more quarters than dimes)
We can rewrite the first problem using the value of Q
D + Q = 15
D + (D+7) = 15
Add the Ds
2D + 7 = 15
Subtract 7 from each side
2D = 15-7 (or, 8)
Divide each side by 2
D = 4
.
Johnny has 4 dimes and 11 quarters.
Now we just count the money.
4 dimes = .40
11 quarters = 2.75
How much all together?
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