A contract between two parties is valid only if one party accepts a legitimate offer from the other; an offer is not legitimate if someone in the position of the party to whom it was made would reasonably believe the offer to be made in jest.
Principle
only if = necessary indicator, put on Right
Contract valid → one party accepts legit offer from the other
if = sufficient indicator, put on Left
Someone being made that offer would reasonably → not legit offer assume offer is in jest
Evaluate
It's common to be given two Principles on Apply the Principle questions, but it's very rare the correct answer uses both principles. Each answer ends up being aimed at one rule or the other.
We want to always arrange our rules so that the "judgy" term is on the right (like good / bad, unjustified / justified, should / should not, etc.).
So we should contrapose that first rule, to get the judgy concept of valid / invalid on the right.
neither party accepts → not valid a legit offer from the other contract
We might notice that the concept of "legitimate offer" shows up in both rules. Does that allow us to chain those rules together? Yes, here it would!
We could say something like,
someone would not a legit not valid assume offer → offer → basis for is made in jest contract
Goal
Although the answer might chain together both rules, if it's anything like 99% of Apply the Principle, it will use one of these rules. The Evidence part of the correct answer will match the trigger of one of the rules, and the Conclusion part of the answer will match the right side of that rule.
Here are our two rules:
1. Neither party accepts → not valid a legit offer from the other contract
2. Someone being made
that offer would reasonably → not legit offer assume offer is in jest
As we look at each answer, we're going to scan for the conclusion. If the conclusion says "not valid", we'll use rule 1. If it says "not legit", we'll use rule 2. If it says anything other than those things, we'll toss it.