SOLUTION: Solve using substitution method For 2000 dollars are bought 15 notebooks and 12 markers. How much does 1 notebook and much does 1 marker cost, if 3 markers cost as much as 6 noteb

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: Solve using substitution method For 2000 dollars are bought 15 notebooks and 12 markers. How much does 1 notebook and much does 1 marker cost, if 3 markers cost as much as 6 noteb      Log On


   

Question 1095810: Solve using substitution method
For 2000 dollars are bought 15 notebooks and 12 markers. How much does 1 notebook and much does 1 marker cost, if 3 markers cost as much as 6 notebooks?
solving looks something like
12x+15y=2000
6y=3x
Please explain thoroughly and step by step :)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = the cost of 1 marker
Let +y+ = the cost of 1 notebook
----------------------------------
(1) +12x+%2B+15y+=+2000+
(2) +3x+=+6y+
--------------------------------
Divide both sides of (2) by 3+
(2) +x+=+2y+
Substitute (2) into (1)
(1) +12%2A%282y%29+%2B+15y+=+2000+
(1) +24y+%2B+15y+=+2000+
(1) +39y+=+2000+
(1) +y+=+51.28+
Plug this result back into (2)
(2) +x+=+2%2A51.28+
(2) +x+=+102.56+
----------------------------
One marker costs 102.56
One notebook costs 51.28
----------------------------
check:
(1) +12x+%2B+15y+=+2000+
(1) +12%2A102.56+%2B+15%2A51.28+=+2000+
(1) +1230.72+%2B+769.2+=+2000+
(1) +1999.92+
OK -error due to rounding off