A school libarian ordered new books for the libary. Of the new books ordered, 1/3 are science, 2/5 are biography, and the rest of the books are fiction. what fraction of the books ordered are fiction?

1/3 and 1/5's denominator would turn into 15 because it's the least common denominator between 3 and 15. So, when you turn it to 15 the numerator changes and you would get 5/15 are science, 6/15 are biographies. Add them together to get 11/15. So, 15-11=4, so 4/15 are fiction.