Question 1119111
Quarters are 5 times as many as dimes: 
q = 5d
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0.25q + 0.10d = 5.40 substitute for quarters, the problem says that q = 5d:
0.25(5d) + 0.10d = 5.40
1.25d + 0.10d = 5.40
1.35d = 5.40
d = 5.40/1.35 = 4
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There are 4 dimes in the box, and since q = 5d, there are 4(5) = 20 quarters in the box