Answer :
12 ≤ x-9
12+9 ≤ x-9+9 ...... adding 9 to both sides
21 ≤ x
x ≥ 21
So if x was an integer for example, then x could be from the set {21, 22, 23, 24, 25, ...}
To graph this on a number line, plot a closed filled in circle at 21. Then shade to the right.
