I'm a very simple person with basic math knowledge. Recently I run into huge problems when calculating how much I spent.
Sometimes to calculate how much I spent I do a calculation $final sum - start sum$. However at other times I do $start sum - final sum$.
When I take the absolute values, are these two values guaranteed to be equal? I've noticed sometimes when I do it one way, or the other way, I get different numbers. Is it because I made a mistake entering the numbers or it's not guaranteed that absolute values are equal?
Somehow I can't reproduce this error today but I just ran into it yesterday. When I did $start sum - final sum$ I got value $y$, but when I did $final sum - start sum$ I got value $z$. I forgot to write down the numbers.