Thanks for the question! So let’s remind ourselves of the rules here. We know that house 3 is a ranch house (from rule 4), and we also know that adjacent houses are of different styles (from rule 1). This means that houses 1 and 5 can’t be ranch houses. So the only other house that could be a ranch house is house 7.
So let’s say house 7 is R, and house 8 is also R. Well, we know that house 6 is S (from the last rule). But notice, there’s nothing else adjacent (next) to house 8 other than house 6. And based on rule 3, every R has to have a T adjacent to it. But that’s not possible since house 6 is a S, not a T. Which means that house 8 can never be a R, and so (A) is not the correct answer choice here.
Hope this helps! Feel free to ask any other questions that you might have.
Christineon June 15, 2021
Hello, why can we eliminate answer choice D? Wouldn't S or R work for placement 7?
Emil-Kunkinon December 1, 2023
From our initial setup, we can tell that 5 must be a t, since it cannot be r or s, and that 8 must be a t, because it can't be another s, and putting an r there would violate the r/t rule. So our initial setup is
_ R T _ _ _ S T
However here, we are given the condition that there are two rs facing each other. The only two that could fit this bill are. 3 and 5, so we have
_ R T _ _ R S T
We also know that since we must have a T next to every R, spot 2 must be T, and cannot be s or r.
