How can I find the version of the Fedora I use?

The proposed standard file is /etc/os-release. See http://www.freedesktop.org/software/systemd/man/os-release.html

You can execute something like:

$ source /etc/os-release
$ echo $ID
fedora
$ echo $VERSION_ID
17
$ echo $VERSION
17 (Beefy Miracle)

cat /etc/issue

Or cat /etc/fedora-release as suggested by @Bruce ONeel

You can also try /etc/redhat-release or /etc/fedora-release:

cat /etc/fedora-release 
Fedora release 7 (Moonshine)

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