When the concentration of a system is changed:

The concentrations change to maintain the original value of K.

The mass action expression changes exponents.

Either the numerator or the denominator of the mass action expression will change.

The equilibrium constant changes.

The concentrations change to maintain the original value of K.

Explanation:

The concentration changes to maintain the original value of K when the concentration of the system changes.

This is the effect concentration has on a reaction at equilibrium.

Le Chatelier's principle proposes that "if any conditions of a system in equilibrium is changed, the system will adjust itself in order to annul the effect of the change".

The equilibrium constant K is temperature dependent. An increase in concentration of a specie favors the direction that uses it up and vice versa. This does not change the value of the equilibrium constant.