SOLUTION:
Case: System of equations
Method:
Let cookbooks be 'c'
and science fiction novel be 's'
$191 in sales for 4 copies of a new cookbook and 5 copies of a new science fiction novel.
191 = 4c + 5s
$148 in sales for 3 copies of the cookbook and 4 copies of the science fiction novel
148 = 3c + 4s

Plug s = 19 in eqn (1)
191 = 4c + 5s
191 = 4c + 5(19)
191 = 4c +95
4c = 191 - 95
4c = 96
c = 96/4
c =24
Final answer:
Cookbook $24
Novel $19