$ sudo apt-get update
$ sudo apt-get install libavahi-core7 

libavahi-core7 is installed in your system.

Make ensure the libavahi-core7 package were installed using the commands given below,

$ sudo dpkg-query -l | grep libavahi-core7 *

You will get with libavahi-core7 package name, version, architecture and description in a table

libavahi-core7 package basic information: