I found useful information related to the questions asked:

1. When did the first cinema open?
   The first cinema opened in 1902.

2. How many cinemas were there by 1907?
   By 1907, there were more than 4000 cinemas.

3. What did audiences listen to while they were watching silent films?
   Audiences listened to a pianist playing live music during silent films.

4. Why did some actors lose their jobs after 192 (likely meaning after 1920s)?
   Actors lost their jobs after the 1920s mainly due to the transition from silent films to sound films ("talkies"). This transition required actors to have good voices and the ability to act and speak on screen, which some silent film actors lacked. The introduction of sound films raised the career termination rates for many silent film actors, as the new technology changed the art and production of cinema. Some actors simply couldn’t adapt to the new demands or had unsuitable voices for sound cinema.

These answers provide a summary about the early cinema era, the growth of cinemas by 1907, silent film accompaniment, and the impact of sound films on actors' careers after the 1920s.