When using interval notation a "[" represents that the number belongs to the interval and a "(" means that the number doesn't belong to the interval, it only limits it. On this case we need to find the interval where the numbers are greater or equal to -11, therefore this number belongs to the interval, and less or equal to -2, this number also belongs to the interval. They belong to the interval, because there is "or equal" on the signals. Therefore the interval can be represented as:
[tex]\lbrack-11,-2\rbrack[/tex]