math
posted by jonathan on .
There are 9 more quarter then dimes.if the total value of the coins is 6.8, how ,any quarters are there?

Is the total value $6.80?
If so, then let Q be the number of quarters and D be the number of dimes.
You know that
Q D = 9, and
0.25Q + 0.1D = 6.80
Solving bu substitution,
0.25Q + 0.1(Q9) = 6.80
0.35Q = 7.70
Q = 22
Now solve for D 
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ty, yw :)