The absolute value of a number is its "distance" from zero. Imagine a number line...notice that -5 and 5 are both equally "far away" from zero. They are both 5 units away from zero.
| -5 | = | 5 |
5 = 5
So...to take the absolute value of a negative number, drop the negative sign.
And to take the absolute value of a positive number, leave it alone.