can someone explain the Gaussian Elimination in very easy terms on how to solve a problem?

can someone explain the  Gaussian Elimination in very easy terms on how to solve a problem? I am not understanding what I am reading on how to do it.

I am trying to solve a problem:

Adam addresses 40 envelopes, stuff 80 envelopes, delivers 75 advertisements, and calls 45 people.

Brittany addresses 80 envelopes, stuffs 50 envelopes, delivers 90 advertisements, and calls 75 people.

Corey addresses 100 envelopes, stuffs 55 envelopes, delivers 45 advertisements, and calls 50 people.

Dane addresses 30 envelopes, stuffs 65 envelopes, delivers 40 advertisements, and calls 80 people.