Somos tres.

There are three of us.

1. Somos 4 en mi familia.
   There are 4 of us in my family.
2. ¿Cuántos sois?
   How many of you are there?
3. Éramos 20 en la obra de teatro.
   There were 20 of us in the play.
4. ¿Cuántos érais?
   How many of you were there?
5. Seremos 100 en la fiesta de despedida.
   There'll be 100 of us at the leaving party.