Explanation
First, the man takes $70 worth of goods from the store's inventory. Second, the shop owner gives the man $30 in change from his own cash register The initial theft of the $100 bill is neutralized because the man uses that exact same bill to pay for the goods, returning it to the owner during the transaction. The 10% tax detail is an irrelevant distraction to the owner's net physical loss of assets. The total loss in value is the sum of the goods lost and the cash given as change: 70 + 30 = 100.
