When previewing the following lines from sonnet 18, how many sentences should readers plan to read fluently? so long as men can breathe, or eyes can see, so long lives this, and this gives life to thee.
a. none
b. one
c. two

The reader should plan to read fluently only one line. The line "So long as men can breathe, or eyes can see, So long lives this, and gives life to thee." There is only one sentence there. The correct answer is B. It is the last two lines of the sonnet, but since there is only sentence, I believe the answer to be One. 

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

answer: x = 4 and y = 4

So far i know that you cant