This is distributive property and to do distributive property, you distribute what is outside of the parenthesis to the numbers inside the parenthesis.
How-to-do:
2(8x-7)
2(8x) - 2(7)
16x-14
17 books in total, and 8 new. To find the number of used books, we subtract 8 from 17.
17-8= 9 used books
Now we have 8 new books and 9 used books.
All books: 17
Used books: 9
New books: 8
(a) all books: used books
17: 9
(b) new books: used books
8: 9
The answer is the first options: y=-2
hope this helps
90 x 7 = 630 square feet total
0.5 fluid ounce per sq ft
630 x 0.5 = 315 fluid ounces are needed