Answer:
It means absolute value.
Explanation:
The lines on the outside of the number just mean absolute value. Absolute value is the distance from zero to the number you want. For example with your problem the answer would be 2.6. A key important fact is that THERE IS NO NEGATIVE DISTANCE. This means that I-2.6I would be 2.6. It is basically the same number but when it is negative you just take away the negative sign. Hope this helps