Thabo owns exactly 140 books, and each book is either paperback fiction, paperback nonfiction, or hardcover nonfiction. if he owns 20 more paperback nonfiction books than hardcover nonfiction books, and twice as many paperback fiction books as paperback nonfiction books, how many hardcover nonfiction books does thabo own?

The no. of hard cover non-fiction , x = 20 books

Solution:

Total no. of books owned by Thabo, t = 140 books

Let the no. of hard cover non-fiction books be x

Then the no. of paper back non-fiction books, y = x + 20

According to the question the no. of paper back fiction books = 2(x + 20)

Now,

x + y + 2(x + 20) = 140

x + x + 20 + 2x + 40) = 140

4x = 80

x = 20

the correct answer is 2.

a slump in geology means a mass movement process of slope failure. a mass of rock or unconsolidated material drops along a slip surface. in other words, rock layers move a short distance down the slope. the slump block is an intact block (2), without any landslide material.

in this image, 1 is the surface of rapture (scarp), 2 the slump block, 3 main scarp (crown), 4 base of rapture with debris flow.

slumps are caused by clear cutting on unstable soils and the sagging of earth, in coastal areas they are due to wave infiltration.

i would say b. research typically uses a variety of sources