Cracking principle and application Qs.

[Aquamarine]

I'm having hard time to solve substitution Qs like PT61,S4,Q19, PT63,S1,Q18 or PT63,S3,Q22.
I've seen these kinds of Qs after PT60.
Whenever I encounter these kinds of questions, I can't usually pick the right answer. I feel much harder than regular principle or necessary assumption questions.

Is there any effective tactic to crack this kind of the Qs?

Please someone enlighten me.
Thanks in advance!

[ManhattanPrepLSAT1]

Hi Aquamarine, great question!

First, rather than looking at them as similar to Necessary Assumptions, approach them more like Sufficient Assumptions. In all 3 of those examples, you're asked to justify an application/conclusion given a stated principle. That means that the principle is not enough to justify the application/conclusion. Your task is to find the gap, the right answer will justify the application/conclusion.

Definitely hone up on your conditional logic skills, my recommended approach would be notating the logic and solving that for the gap.

Good luck!