Answer:
1. Ustedes deben recordar el poema.
2. Yo voy almorzar a la una.
3. El camarero le sirve al hombre.
4. Frederico y Yo repetimos las frases.
5. Tu tienes que regar las flores.
Translation:
1. You must remember the poem.
2. I will eat lunch at one.
3. The waiter serves the man.
4. Frederico and I repeat the sentences.
5.
You have to water the flowers.
The number that is not like the others is 16. All of the other numbers are divisible by 3. (21/3 = 7, 15/3 = 5, 6/3 = 2, 27/3 = 9)