Question 1009120
Call the numbers of dimes and quarters, d and q.  Thus we have
d + q = 28  and the value equation is
10d + 25q = 460   (we work in cents)
Now multiply the top equation by ten and subtract...we get
10d + 25q = 460
-(10d + 10q = 280)
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15q = 180
q = 12 quarters
d = 16 dimes