Explain, using a real-world example of debt, why subtracting a negative number is the same as adding a positive number (e.g., 10 - (-5) = 15).

Subtracting a negative number is equivalent to adding the corresponding positive number, because subtracting a debt means removing the debt, and removing debt makes you richer.

Real-world example :

Suppose you have ₹10 in your wallet and someone has previously recorded that you owe (debt) ₹5 to them.

Your effective wealth in this situation = ₹10 - ₹5 = ₹5.

Now, suppose your friend cancels (removes) the debt of ₹5 (that is, subtracts -5 from your account).

After cancellation :

⇒ 10 - (-5)

⇒ 10 + 5

⇒ 15.

So, removing the debt of ₹5 effectively increases your wealth by ₹5, making your total ₹15.

Hence, subtracting a negative number is the same as adding a positive number, because removing a debt is equivalent to gaining wealth.