Final answer:
The two numbers four units away from 0 on the number line are -4 and +4; one is to the left, and the other is to the right of 0.
Step-by-step explanation:
The two numbers that are 4 units away from 0 in any direction on the number line are -4 and +4. This is because the distance from 0 to a number is measured by the absolute value.
The negative number -4 is 4 units to the left of 0, and the positive number +4 is 4 units to the right of 0. Therefore, both -4 and +4 satisfy the condition of being 4 units away from 0 on the number line.