The library has added 160 scientific and technological books, which is 20 times less than story books. How many story books are there?

Solution: let the storybook be X.

4x-20= 160

x=45

There are 45 story books.

If you haven't learned to set X.

Then the direct algorithm is that there are 20 fewer science and technology books than 4 times story books, so 4 times science and technology books are equal to +20 science and technology books.

The formula is

( 160+20)/4=45

There are 45 story books.

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