The correct answer is S. The sequence is each alternate letter, changing from one end of the alphabet to the other.
Z Y X W V U T S R Q P L M N O K J I H G F E D C B A
Since we started at the end of the alphabet and then went back to the beginning, there are two letters in the middle that aren't part of the pattern. We only need to worry about which letter is next at the end of the alphabet, though, and the next highlighted letter after U is S.
Hope this helps!
The solution to a system of (linear) equations is the point where the graphs intersect. Consider two parallel lines. By definition, two parallel lines never intersect each other, but all pairs of non-parallel lines will eventually intersect. That means they will also have a solution.
Let's consider what makes a line parallel to another line. It basically looks identical, having the same steepness (slope), but the graph is just shifted over. That is, a parallel line would have the same slope and a different y-intercept. For our equation

, or

in slope-intercept form, a parallel line will be of the form

.
That describes the form of a parallel line, which we do not want. Any other line, however, will give a solution to our system, so we merely want a line where the slope does not equal 2.
We can have any equation of the form

.
2 3/4a=19 1/4
÷2 3/4 ÷2 3/4
a=1/7
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- I think it's possibly this "The figure must be a square because the diagonals of a square bisect the right angles." but there's also "The figure must be a rhombus because it has exactly 2 pairs of congruent angles." buuut since the first one seems more better i'm assuming then that's probably the right answer.