Thirty.
3 seconds sound clip from the The Big Trail (1930) movie soundboard.
You can hear this line at 00:20:52 in the Blu-ray version of the movie.
Quote context
[...]
- Honey Girl, it's time for your history lesson, dear.
- Now, uh, how many stars in the flag?
- Thirty.
- Now, who discovered the Columbia River?
- Honey Girl, it isn't safe to be sitting in a rocking chair, when there are certain persons present.
- I think you'll find we have everything.
[...]