Can someone help me understand this logic?

Star Platinum

"Unless Shiming's car is fixed, which cannot happen without Steve's help, there will be no road trip next week."

From the lesson, https://7sage.com/lesson/quiz-complex-conditional-translations-4-w-answers/

I'm very confused in here because of the prior rules of mixing group 3 and group 4 conditional indicators. And in this sentence there's a bunch of them.

I understand the "final" necessary condition being /road trip next week. So the first conditional statement written in logic would be /car fixed > /road trip. This part I understand as we are using group 3 logic, negate sufficient. Simple enough.

Now to add the second part, "Unless Shiming's car is fixed, which cannot happen without Steve's help....."

In this sentence we have two group 3 indicators and one group 4 indicator. What do we do in this situation? In a previous lesson when we run into this situation, we pick one side, follow that group's negation rules, then treat the other "logical indicator" as a negation.

So for example, I want to follow group 3's rule on the indicator "unless". Which is choose a side, make it the sufficient condition, and negate. Okay. Let's pick car fixed.

So this puts me at /car fixed > which cannot happen without Steve's help.....

Now on the necessary side we have a group 3 and a group 4 logical indicator in there :DDDD.

What do we do here? If I treat both as a negation which cancels each other out, that turns into /car fixed > Steve's help. Which makes absolutely no sense at all. And even the other way around, /car fixed > /steve's help, which makes so much more sense, it doesn't fit in the final answer. This is because the contrapositive of /car fixed > /steve's help is steve's help > car fixed.

The final answer being /steve's help > /car fixed > /road trip. The contrapositive being road trip > car fixed > steve's help.

Help me please~~~

melsathope

Unless Shiming's car is fixed, which cannot happen without Steve's help, there will be no road trip next week.

Let's try to rewrite the first part: the "which" refers to the first part of the sentence "unless Shiming's car is fixed". The "cannot" specifically refers to the "car is fixed". Meaning, the car cannot be fixed without the help.

This sentence can be translated to:
Without Steve's help, Shiming's car cannot be fixed. Unless Shiming's car is fixed, there will be no road trip next week.

Let's start in order.
Without Steve's help, Shiming's car cannot be fixed.
I will use "/" as a "no" like you did in the discussion post...
/Steve's help > /fixed
why did I do this? Because that's what the sentence says.

If no help, no car fixed. Simple... No need to switch things around here. Ok, next part of the sentence.

When translating "A unless B" statements: Negate A and maintain B. Examples:

a) I will wear my new jacket, unless it rains.
Not wear new jacket > rain

b) I will bring my dog to the vet, unless he fells better.
Not bring to the vet > feels better

In the same token, because you need to negate the "A" part, if the A part in the original statement is already a negation, then you need to make it positive. Examples:

a) I will not wear my new jacket, unless it rains.
Wear new jacket > rain

b) I will not bring my dog to the vet, unless he feels better.

Bring dog to the vet > feels better

So going back to the original statement:
Unless Shiming's car is fixed, there will be no road trip next week.
A unless B, which is the same as Unless B, A (which is the format for this sentence).
So, we want to negate "A" which is "there will be no road trip next week":

there will be NO road trip translates to "there WILL BE a road trip":
road trip > ???
we want to maintain the original "B" statement as is, so:
road trip > fixed

ok so now combining the two statements:
/Steve's help > /fixed
road trip > fixed

opppsiiieee.. We can't combine this way. So let's contrapositive either one of the statements so we can combine them:

/Steve's help > /fixed changes to fixed > Steve's help

so now combining:

road trip > fixed > help

the contrapositive is:

/help > /fixed > /road trip