Count the distance d, which gives you 7.
Use Pythogarean theorem to find c:

Plug in the numbers:

c is 5.
Same thing with g:

g equals 5.66.
Answer:
79 books
Step-by-step explanation:
45% books not returned = 55% books will be returned
145 books currently checked out
55% of 145 = 79.75
since you can't return 3/4 of a book, i would round down to 79.