1352

[KennethC991]

Why is the second choice wrong here?

Please help.

[ohthatpatrick]

Sorry for the delay.

I have no way to access these arcade problems by number (I have to email our techsupport to get an image emailed back to me), so in the future if you can copy the question over, you'll get a faster response.

In Games, whenever you see these BUT NOT BOTH ordering rules, it will always give you two different ways of seeing three characters.

"R is either before S, or after P, but not both"

You were asking why we can't represent that as
S - R - P
or
P - R - S

Well, we can't do S - R - P, because NEITHER of the conditions were met. R is NOT before S and R is NOT after P.
we can't do P - R - S, because BOTH conditions are met. R is before S and R is after P, and we were told we CAN'T have BOTH.

When R is before S, we CAN'T also have R after P.
So you write out
R - S
and you think, "In this world, R can NOT be after P. Thus R is BEFORE P."

So R is before S and before P in this world.

In the world where R is after P, we can NOT also have R before S.
So you write out
P - R
and you think, "in this world, R can NOT be before S. Thus, R is AFTER S."

So, R is after P and after S in this world.

Hope this helps.

p.s.
had the rule said
"R is before P or before S, but not both", then we would have symbolized the rule as
P - R - S
or
S - R - P