Answer
There are 495 different combinations.
Explanation
Picking 4 books to read out of 12 books, with the order of picking unimportant is evaluated as ¹²C₄
[tex]\begin{gathered} ^{1}^{2}C_{4}=\frac{12!}{4!(12-4)!}=\frac{12!}{4!\times8!}=\frac{12\times11\times10\times9\times8!}{4!\times8!} \\ =\frac{12\times11\times10\times9}{4\times3\times2\times1} \\ =495 \end{gathered}[/tex]
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