Joel bought 2 notebooks, 3 pencils, and 6 files for $12.70. The cost of 1 pencil and 2 files is $4. What is the cost of 1 notebook?
+180 Joel bought 2 notebooks, 3 pencils, and 6 files for $12.70. The cost of 1 pencil and 2 files is 4. What is the cost of 1 notebook?
Let's assume notebook = n, pencils = p, and files = f
2n+3p+6f = $12.70
1p+2f = $4
We know that 1p+2f = 4$ so that means that 2p+4f = 8$ and 3p+6f = 12$.
As you can see 3p+6f = 12$ so we can subtract that from the 2n+3p+6f = $12.70 which we get
2n = $.70
Therefore n = $.35
Hope this helps! 
