> apt-cache search gtk+-3.0
[...]
libgtk-3-0 - GTK+ graphical user interface library
libgtk-3-0-dbg - GTK+ libraries and debugging symbols

25 upgraded, 15 newly installed, 0 to remove and 21 not upgraded.
Need to get 18.9 MB of archives.
After this operation, 12.6 MB of additional disk space will be used.