A mixture is a substance that is made up of 2 or more substances that are not chemically combined together, which means they can be separated without going through chemical processes, like heating or electrolysis. They can be separated just by simple physical methods such as filtration.
Since a can of peas and carrots is composed of pea and carrots, which both of them are not chemically combined, and can be separated without being heated or applying electricity, therefore, it is a mixture.
