SOLUTION: a student bought 23 cent, 41 cent, and 80 cent stamps with a total value of $31.50. if the number 23 cent stamps is 2 more that the number of 41 cents stamps, and number of 80 cent

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Question 630165: a student bought 23 cent, 41 cent, and 80 cent stamps with a total value of $31.50. if the number 23 cent stamps is 2 more that the number of 41 cents stamps, and number of 80 cent stamps is 5 more than one half the number of 41 cents stamps, how many stamps of each denomination did the student obtain?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = the number of 23 cent stamps
Let +b+ = the number of 41 cent stamps
Let +c+ = the number of 80 cent stamps
given:
(1) +23a+%2B+41b+%2B+80c+=+3150+ ( in cents )
(2) +a+=+b+%2B+2+
(3) +c+=+b%2F2+%2B+5+
-----------------
Substitute (2) and (3) into (1)
(1) +23%2A%28+b+%2B+2+%29+%2B+41b+%2B+80%2A%28+b%2F2+%2B+5+%29+=+3150+
(1) +23b+%2B+46+%2B+41b+%2B+40b+%2B+400+=+3150+
(1) +23b+%2B+41b+%2B+40b+=+3150+-+46+-+400+
(1) +104b+=+2704+
(1) +b+=+26+
and, since
(2) +a+=+b+%2B+2+
(2) +a+=+26+%2B+2+
(2) +a+=+28+
and
(3) +c+=+b%2F2+%2B+5+
(3) +c+=+26%2F2+%2B+5+
(3) +c+=+13+%2B+5+
(3) +c+=+18+
There were 28 of the 23 cent stamps
There were 26 of the 41 cent stamps
There were 18 of the 80 cent stamps
check:
(1) +23a+%2B+41b+%2B+80c+=+3150+
(1) +23%2A28+%2B+41%2A26+%2B+80%2A18+=+3150+
(1) +644+%2B+1066+%2B+1440+=+3150+
(1) +3150+=+3150+
OK