Answer:
1. Tengo miedo. Creo que la motocicleta no _es segura___. está segura es segura es seguro está seguro
(I'm afraid. I don't think the motorcycle is safe.)
ES because it's a propery of the motorcycle.
SEGURA because 'motocicleta' is femine
2. Yo ya __estoy lista __ para salir. ¿Y Miriam? estoy lista está lista soy lista es lista
(I'm ready to leave. And Miriam?)
Being ready to leave is something you are at a given moment, it's temporary, not permanent.
3. ¿Dónde __están __ nuestros pasaportes? están es está son
(Where are our passports?)
Their location is temporary, so estar.... and it's plural since it's 'passportes'.
4. La habitación __está sucia__. es sucio está sucio está sucia es sucia
(The room is dirty)
The fact that the room is dirty is a temporary condition, not an inherent trait of the room.... so 'estar'. La habitation is feminine... so 'sucia'.
5. La reunión (meeting) con la agente de viajes __es __ a las cuatro de la tarde. son es están está
(The meeting with the travel agent is at 4 PM)
The time of the meeting is something inherent to that meeting... so it's SER. The subject is the meeting, so it's singular (ES not SON).
6. Mi maleta __es pequeña__. es pequeña está pequeña es pequeño está pequeño
The size of an object is something inherent to that object, it will rarely change with time... so it's SER.
Mi maleta is femine... so pequña.
7. ¿Dónde _está _ la salida? es está están son
When you talk about a location, it's always ESTAR... even if it's a permanent location.
The subject is salida... so singular.