To solve this problem, let's first find the number of pages Javier still needs to read in order to finish the book.

Method 1: Subtraction

We can subtract the number of pages Javier has already read from the total number of pages in the book:

$\text{Pages remaining} = \text{Total pages} - \text{Pages read}$

$\text{Pages remaining} = 542 - 396 = 146$

So, Javier needs to read 146 more pages to finish the book.

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Method 2: Finding the difference in fractions

Another way to approach this problem is to think about the proportion of the book he has already read, and how much is left. We can calculate the fraction of the book he has read and then find how much remains.

1. First, find the fraction of the book he has read:

$\text{Fraction read} = \frac{396}{542}$

2. The fraction of the book left to read is the remainder:

$\text{Fraction left} = 1 - \frac{396}{542} = \frac{542 - 396}{542} = \frac{146}{542}$

3. To find the number of pages he still needs to read, multiply the total number of pages by the fraction left:

$\text{Pages remaining} = 542 \times \frac{146}{542} = 146$

So, this method also shows that Javier needs to read 146 more pages.

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Would you like more details or have any questions?

Here are some related questions you can explore:

1. If Javier reads 20 pages every day, how many days will it take him to finish the book?
2. How much of the book has Javier already read as a percentage?
3. If Javier had started with 100 pages read, how many pages would he need to read in total to finish?
4. How many pages has Javier left as a fraction of the total number of pages in the book?
5. If the book has 600 pages, how many more pages would Javier need to read if he has read the same 396 pages?

Tip: When dealing with problems about parts of a whole, it's useful to break it down into subtraction or fractions to easily find the remaining part.