Which piece of evidence best illustrates the impact of the villagers' actions? A. "You might bring down a curse on us. Lay off,' warned an old man, but the
younger one energetically threw the pebble in." (Paragraph 12)
B. "Better than dumping all of its garbage in the ocean, went the thinking in the
city, and plans were made for a long pipe to carry it to the hole." (Paragraph 37)
C.
“The police felt comforted as they used the hole to get rid of accumulations of
expertly done counterfeit bills." (Paragraph 39)
D. "He thought it must be his imagination. Then, as he resumed his former
position, from the direction where the voice had come, a small pebble skimmed
by him and fell on past." (Paragraph 44)

quite an interesting way to teach topic sentences, because the answer to this question is the best definition of a topic sentence that one can present, it is as if answering the questions taught you how to do it, this is some real teaching, it is terribly well-done.

the topic sentence in this paragraph is:

topic sentences writers stay on track and keep a paragraph from becoming an aimless collection of sentences about an idea.

which incidentally tells you what a topic sentence should be.

substitute y = 2x - 4 to x + 2y = 12:

x + 2(2x - 4) = 12     use distributive property

x + (2)(2x) + () = 12

x + 4x - 8 = 12     add 8 to both sides

5x = 20     divide both sides by 5

x = 4

put the value of x to the first equation:

y = 2(4) - 4

y = 8 - 4

y = 4