how would you use substitution to figure out #26 on test 4 page 722?

Start by plugging in the first numbers that occur to you that work. How about x = 2 and y = 3? That works, because –3 < 2 < 3.

Does that eliminate any of the Roman numerals?

I. |2| < 3
II. 2 > 0
III. 3 > 0

Hmm…it does not. The next step is to think about whether you can make any changes to the numbers you chose that would still make the main condition true, but that might break one of the Roman numerals. This just requires a bit of creativity and the experience of having done questions like this before .The Roman numerals give it away a bit: you need to test if x or y can be negative.

As it turns out, x totally can: x = –2 and y = 3 works fine: –3 < –2 < 3. That shows that Roman numeral II doesn’t have to be true.

To really be sure that III is true, recognize that the question is telling you that –y < y. Can that be true if y is negative? No, it cannot. Therefore, y must be greater than 0, and the answer is C.