Question

Okay hear this someone came into my shop and stole $100 without my knowledge they came back to the store and spent $70 in items i gave $30 back how much money did i lose ?

Answer 1

The Answer would be $100
'cause that $70 which he spent on your shop would give some supplies to him in exchange.
So, for final, you lose $100.

Answer 2

You lost thirty dollars