You were half right - you're correct in your first (sequencing) example, but incorrect on your second (in/out) example. To find the contrapositive, flip and negate. Here's what that means:

You gave the example of "If X is 3rd, then Y is 5th."

X in 3rd is your sufficient condition (left side), Y in 5th is your necessary condition.

X3 -> Y5

To flip them, you move them to the opposite sides of the lawgic equation - X3 moves to the right side (necessary side), Y5 to the left side (sufficient side). But to get the contrapositive, you also have to negate them. It becomes:

/Y5 -> /X3

(If Y is not 5th, then X is not 3rd.)

These are the only statements you can come up with from that initial statement ("If X is 3rd, then Y is 5th.") The sufficient condition triggers the necessary condition, but the mere presence of the necessary condition doesn't actually tell you anything about the sufficient condition. If you know Y is 5th, that doesn't tell you anything about X - it could be 3rd, or it could be in another position. Similarly, if you know X is NOT 3rd, that doesn't tell you anything about Y - it could be 5th, or it could not be. The right side of your lawgic equation doesn't do anything to the left side.

For your In/Out example, the contrapositive of X in -> Y in IS NOT X out -> Y out. Please don't do that to yourself! You've got to flip your variables and negate them, and in this case you didn't flip them. Here's the lawgic for "If X is in, then Y is in."

X -> Y

/Y -> /X

(in other words:

X in -> Y in

Y out -> X out)

X out is on the right side. It's the necessary condition. It doesn't tell you anything about Y.

(Y in also doesn't tell you anything about X. But Y out tells you that X is out.)

7Sage Flex is just picking the first of the two LR sections - so if the LR sections were 2 and 3, you'll take the section 2 LR.

For the Flex, LSAC is using existing LR sections from non-disclosed tests. As far as anyone can tell, they aren't mixing and matching LR questions from different sections to create a Frankenstein version. On the test day, you may get an "easier" section or you might get a "harder" one - it just depends on what LR section you get of the handful they've decided to use, which is partially based on the time you schedule your test. They're swapping different sections in throughout the weekend/week as people are testing - there's not one August Flex, one October Flex, etc. There are lots of different versions, so the test that someone takes at 10am on October 3rd could be completely different than the one someone else takes at 4pm on October 4th (or it could have sections in common).