"Not that shirt, the other one."
Translation:Esa camisa no, la otra.
Duolingo, please add this answer as well: 'no esa camisa, la otra', thanks
"One" is often built in to other words: la otra (the other one), Me gusta ese. (I like that one.) Voy a comprar la roja. (I'm going to buy the red one.) English seems to like the word "one" where it isn't always needed in Spanish.