<PRE><B>Question 974014</B>
Set D = number of dimes
Q = number of quarters
0.25 * Q + 0.10 * D = 3.75
D + Q = 21
Solve the last equation for D by adding -Q to each side
D = 21 -Q
Substitute (21 -Q) for D in 0.25 * Q + 0.10 * D = 3.75
0.25 * Q + 0.10 * (21 -Q) = 3.75
0.25Q + 2.10 - 0.10Q = 3.75
0.15Q + 2.10 = 3.75
add -2.10 to each side
0.15Q = 1.65
divide each side by 0.15
 Q = 11
Since there are 21 coins, we have 10 dimes.
11 quarters = 2.75
10 dimes = 1.00
Total is 3.75
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