We can think of temperatures above zero F and below zero F. For example weather conditions in cold places like Alaska.
In the morning, the temperature could be 2 degrees F (above zero)), but later towards the night, the temperature could be below zero in three units : -3 degrees F.
So the difference is the distance from zero to 2 (above) and the distance to zero from below 3 (below the zero mark. so these two differences from zero add up as 2 + 3 = 5
The way to do such in one go with math is to write the "difference" (normally associated with a SUBTRACTION, of the form: 2 - (-3), and therefore use that the negative (or opposite) of a negative number is a positive number:
- (-3) = +3
The same happens when we want to compare the difference between
9 - (-15) = 9 + 15 = 24
with the difference:
-15 - 9 = -24
The important thing is to consider the absolute value if we just want to find the number of units between the values, how many units they are separated.
And if we need to find what needs to be added or subtracted to one of them, at that point the sign of the difference is critical. This is because in one case we will need to add to get to the other number, while in the other case we need to subtract.