Asystem in which people make, exchange, and use things that have value is

The answer to this is trade as trade is the exchange of products between countries or people that involve items of value. These products might be abundant in some countries but not in others.

the answer is bartering.

I hope this helps.

answer; seasons change because earth tilts on its axis; and the angle of the tilt causes the northern and southern hemisphere to trade places throughout the year;