You liked some shirt that costs $97.

You borrowed $50 from your mom and $50 to your dad.

How much you got? $100.

You bought the $97 shirt, how much is the change? $3

You returned the change ($1 for mom & $1 for dad), how much is left with you? $1

Here's the question:

50 (from dad)
+50 (frm mom)
-------------
100
-97 (cost of shirt)
----
3 (change)
- 1 (change for mom)
- 1 (change for dad)
-----
1 Why there's an excess?

I'm not sure I follow you? Its simple math, what is the question exactly?

Why there's an excess of $1?

I normally don't come here to the math forum, but I was interested in your question. But the question is it's own explanation. You lay it out. Unless I'm missing something.

I don't know the answere either. Do the counting yourself.

Well, maybe I'm a bozo, but you either have to give your parents $1.50 each or you keep the excess for yourself. Do whatever you want with it.