For most adjectives, the endings are like this:
o : masculine singular
os : masculine plural
a : feminine singular
as : feminine plural
La abuela means the grandmother. It is a feminine singular word. Therefore, you use the ending -a, so the answer is vieja.
Also, keep in mind that the adjective endings match noun endings. Abuela has the ending -a, so the adjective should also end in -a.
Answer:
1. espera
2. preguntamos
3. cenas
4. llevan
3. Ellas ensenan administracion de empresas.
Yo necesito preparar la tarea.
Hector y yo compramos libros en la libreria.
A mi me gusta bailar los sabados.
Enrique desea escuchar musica.
A ti te gusta la psicologia.
Explanation: