college algebra word problem

Question

In one day, a book store earned $239 in sales for 4 copies of a new cookbook and 5 copies of a new science fiction novel. On the next day, it earned $182 in sales for 3 copies of the cookbook and 4 copies of the science fiction novel. What was the price of each book?

Answer 1

1st equation: 4C + 5S = 239

2nd equation: 3C+ 4S = 182

multiply 1st by 3 and multiply 2nd by 4, then subtract 1st from 2nd, to eliminate C

12C +16S = 728

12C +15S = 717

_________________

S = $11 for science fiction book

3C = 182-4(11) = 138

C = 138/3 = $46 for cook book