draw your number line and mark it as usual
put your pencil on 4
now move 4 units to the left (subtract)
where are you now?
4 units to the left of 4?
2 answers
4 units to left = 4-4 = 0.
4 units to the right = 4+4 = 8.
4 units to the right = 4+4 = 8.