One of the strings of the guitar is broken. Do you want to change it at the musical instrument store? how much is it?

As long as it is a more formal musical instrument store, it will be changed.

If you are familiar with the musical instrument store, it is generally free to change strings;

If you are not familiar with musical instruments, it depends on what your guitar looks like:

The strings of folk songs are generally very cheap, just a few dollars, or the old strings will be exchanged for you for free;

The strings of classical guitars should be good or bad, almost a dozen pieces, and if they are good, 100 pieces or so.

Of course, if the video store doesn't change it for you, there's nothing you can do. And even if he changes it for you, you'd better ask while watching and learning. Self-study is the right way.

Generally speaking, you can pay the bill, but you'd better buy a set and keep it, so as not to go to the music store again. 1 string, 2 strings, it is best to buy two more strings, which is the easiest to break.