Answer:
X is moving into the cell by active transport
Step-by-step explanation:
According to Oxford dictionary;active transport refers to ''the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy''.
Since the concentration of X is higher inside the cell than it is outside the cell, energy must be required in order to move substance X across the cell membrane against existing concentration gradient. This process is called active transport.