Luckily for us, this problem solved the bulk of its own question!
Now, all we have to do is solve for "x", or the amount of fiction books and plug its value back into the original equation to find the value of "y", or the amount of nonfiction books.
2x = 38
x = 19
There are 19 fiction books.
x + y = 26
19 + y = 26
y = 7
There are 7 nonfiction books.
Hope this helps!