Question

Henry has twice as many fiction.

books as non-fiction books. He has
17 more fiction books than non-fiction
books. How many books does Henry
have in all?​

Answer 1

Let
`x` be the number of non-fiction books. We deduce that the number of fiction books is
`2x`, since they are twice as much.

Since the difference between the two numbers is 17, we have

`2x-x=17\iff x=17`

So, Henry has 17 non-fictional and 34 fictional books, for a total of 51 books.