Posted by selena on Sunday, March 8, 2009 at 10:33pm.
lavre has sixtyone coins, all of whichare dimes and quaters. if the total value of the coins is $9.85, how many of each kind of coins has she?

grade 9 math!!!!!!!!!! please help  DrBob222, Sunday, March 8, 2009 at 10:49pm
If Q = # quarters
and D = # dimes.
Then
Q+D=61
.25Q+.10D=9.85
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Two equations and two unknowns. Solve for Q and D. Check my work. 
grade 9 math!!!!!!!!!! please help  Anonymous, Monday, March 9, 2009 at 1:33pm
Q = 25
D = 36
It's a system of linear equations so you can put it into a matrix to solve
let Matrix A be a 2x2 matrix
1 1
.25 .1
and have another matrix, B
61 
9.85
A^1 * B will give you the answer