Final answer:
The opposite of a number that is 12 units to the left of 0 is 12 units to the right of 0 on the number line. This number is positive 12, as it is the same distance from the origin but in the opposite direction.
Step-by-step explanation:
A number that lies 12 units to the left of 0 on a number line would be at the position of -12. The opposite of this number is the number that is the same distance from 0 but in the opposite direction on the number line. Therefore, the opposite of -12 is 12, which lies 12 units to the right of 0 on the number line.
This is visually represented on a number line where moving to the left of 0 indicates a negative value, and moving to the right indicates a positive value. When asked to locate the opposite of a number on the number line, you always look to the same distance from zero but in the contrasting direction. In this case, since the original number is 12 units to the left, its opposite will be horizontally on the coordinate system to the right side, 12 units away from the zero point.