Look at the pictuse below i would copy and paste but I can't copy a picture

15

Step-by-step explanation:

The constant of proportionality is 15 books per shelf.

If you look at the graph, you can see that for every 1 shelf, there are 15 books. For 1 shelf, there are 15 books, and for 2 shelves, there are 30. And the pattern continues.

Let me know if you have any questions, thanks!

x = ± 6i

step-by-step explanation:

x^2 = -36

take the square root of each side

sqrt(x^2) = sqrt(-36)

we know sqrt(ab) = sqrt(a) sqrt(b)

x = ±sqrt(36) sqrt(-1)

we know that sqrt (-1) = i

x = ± 6i