How can i justify my answer in words in the problem -5 - 3 = -8?

Answer 1

Subtracting Positive Numbers

Subtracting positive numbers is just simple subtraction.

Example: 6 - 3 = 3
is really saying
"Positive 6 minus Positive 3 equals Positive 3"
You could write it as (+6) - (+3) = (+3)

Answer 2

Subtracting a Negative is the same as Adding


Ally can be naughty or nice. So Ally's parents have said

"If you are nice we will add 3 points (+3). If you are naughty, we take away 3 points (-3). When you reach 30 Points you get a toy."

Ally starts the day with 9 Points:


Ally's Mum discovers spilt milk: 9-3 = 6

Then Dad confesses he spilt the milk and writes "undo". Mum calculates: 6-(-3) = 6+3 = 9


So if you subtract a negative, you gain points
(ie the same as adding points).

Answer 3

subtract 3/4 of a cent from $.4900