The word problem: Two friends owe me \$20. One friend owes me \$5 more than the other. How much does each friend owe me?
My equation: $y + y + 5 = 20$
My colleague's: $-y + -y+5 = 20$
I understand that we commonly use the - sign for owing money. But if your answers end up being -\$12.50 and the other -\$7.50, you can't owe a negative amount of money, right? You'd have to keep everything positive, and then state that "each owes \$7.50 and \$12.50, respectively", right? Or am I off on this?