The results were as follows: 43 had used the Kindle, 52 had used the iPad and 35 had used the Nook. Thirteen students had used the Kindle and iPad, 14 had used the iPad and Nook and 12 had used the Kindle and Nook. Five students had used all three readers. Determine how many of those surveyed had used:
a.exactly one of these readers.
b.none of these readers.
c.at least two of these readers.
d.the Kindle and iPad, but not the Nook.
e.the Kindle or iPad, but not the Nook.
f.only the Kindle.
См. статью: A survey was taken of 180 college students to see which electronic reader they had used?