| 9 - 3g | ≤ 12
This is an example of absolute equality
it could be solved as follows:
9-3g ≤ 12 and -(9-3g) ≤ 12
-9+9-3g ≤ 12-9 and -9+9+3g ≤ 12+9
-3g ≤ 3 /-3 and 3g ≤ 21 /3
-1 ≤ g and g≤ 7
so the interval [-1,7] is the solution to your inequality
hope that helps
