Answer
$0.363$
Work Step by Step
Number of choices of selecting 3 out of 8 science books: $_8C_3$=56
Number of choices of selecting 4 out of 9 math books: $_9C_4$=126
Total choices of selecting 7 books out of 17: $_{17}C_7$=19448
The probability for this problem $p=56\times126/19448=0.363$