"The sister is in the city; the mother is at home."
Translation:Soror in urbe est, mater domi est.
I think Latin likes to "compress" where possible (= leave out unnecessary words), so I would expect "Soror est in urbe, mater domi" (with only 1 appearance of "est").
Or maybe: Soror in urbe, domi mater est. (with juxtaposition of the two locations, for better contrast; and the verb appearing just once)