What's the correct change?

Question

Ok my mom has a20$ and she's wanting change for it so I said mom I have 2 5$ and she hands me the 20$ is that the correct math for that or do I owe her 10$ still?

Answer 1

You still owe her $10

You got $20 and gave her 5+5 = $10

You're $10 ahead, she's $10 behind. You owe her $10, unless she needed change so much that she made you a gift of the ten. Or maybe you gave her something worth $10 and she gave you $20 expecting change of $10. Then you don't owe her anything,