Of the books in a library, 1/3 came from robbie's collection and 15 came from marta's. of the rest, 15 were elena's 1/5 were winfield's, and 5 were purchased from the bookstore. how many book are there in the library?

Library amount: l
Robbie: r=(1/3)l
Martha: m=15
rest of books: l-r-m=e+w+b
Elena: e=15
Winfield: w=1/5(e+w+b)
bookstore: b=5

w=(e+w+b)/5
w=(15+5+w)/5
w=4+w/5
(4/5)w=4
w=5

l-r-m=e+w+b
l-(1/3)l-15=15+5+5
(2/3)l=25+15
(2/3)l=40
l=60=amount of books

It has a slope of 1 nd a y intercept of -2