"There is a rat outside the house."

Translation: घर के बाहर एक चूहा है।

[BriannaBir4]

why can't the sentence start with "chuha"? I did subject - post-positional phrase - verb and it was counted wrong

[zeebo7]

It's subtle, but that would be 'A rat is outside the house'.
घर के बाहर एक चूहा है is the translation for "There is a rat outside the house" (or, equivalently, "Outside the house there is a rat".).

Anyway, I would say yours should probably be accepted anyway, so maybe report it if it comes up again.

[OJFord]

Not accepted with मकान instead of घर, it should be I think? Have reported.

[bhairabsaikia]

Why is it घर के बाहर and not घर का बाहर?please answer.

[OJFord]

Because घर is in the oblique case here - I won't dare to say it's impossible to form a sentence with 'का बाहर', but usually it will be के, as with के साथ।