Update Manager of Linux Mint 18 recently gave me an error:

Repository 'http://dl.google.com/linux/chrome/deb stable Release' changed its 'Origin' value from 'Google, Inc.' to 'Google LLC'

While I was trying to update Linux Mint. The problems seems to be caused by updated related to google-chrome-stable and change of Google name:
Google parent Alphabet forms holding company

A quick fix to this problem will be to ensure that the new entity named Google LLC you are fetching Google Chrome updates from is the same as Google, Inc. that your system trusts and knows its signature.

sudo apt update

and then simply type 'y' to accept the offered change.

Example output of the command:

E: Repository 'http://dl.google.com/linux/chrome/deb stable Release' changed its 'Origin' value from 'Google, Inc.' to 'Google LLC'
N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
Do you want to accept these changes and continue updating from this repository? [y/N] y

Note that apt-get will not help you to solve this problem.

sudo apt-get update

More information about apt and apt-get: The Debian Administrator's Handbook

APT is a vast project, whose original plans included a graphical interface. It is based on a library which contains the core application, and apt-get is the first front end — command-line based — which was developed within the project. apt is a second command-line based front end provided by APT which overcomes some design mistakes of apt-get.
Numerous other graphical interfaces then appeared as external projects: synaptic, aptitude (which includes both a text mode interface and a graphical one — even if not complete yet), wajig, etc. The most recommended interface, apt, is the one that we will use in the examples given in this section. Note however that apt-get and aptitude have a very similar command line syntax. When there are major differences between apt, apt-get and aptitude, these differences will be detailed.