Given the inequality:

You can identify that the symbol of the inequality is:

It means "Less than or equal to".
To write the solution in Interval Notation, it is important to remember the following:
1. You must use parentheses when a value is not included.
You can identify when a value is not included because the inequality has one of the following symbols:

2. You must use square brackets when a value is included.
You can identify this when the inequality has one of these symbols:

In this case, you can identify that -6 is included.
Since "x" is less or equal to -6, there is no endpoint to the left of -6. It goes indefinitely to the left of that number.
Therefore, knowing the explained before, you can write the solution in Interval Notation as follows:
![\mleft(-\infty,-6\mright]](https://img.qammunity.org/2023/formulas/mathematics/college/suwcz0szzqlk5q59mqdsyntlg6s108nlc2.png)
Hence, the answer is:
![\mleft(-\infty,-6\mright]](https://img.qammunity.org/2023/formulas/mathematics/college/suwcz0szzqlk5q59mqdsyntlg6s108nlc2.png)