Question

A customer has $75 worth of vouchers to spend in the gift shop.

She buys gifts costing $143.

If the voucher is used, how much more money will the customer need to pay for the gifts?

Answer 1

Just subtract $75 from $143; you'll get a negative result:  -$68.  This means that the customer has to come up with $68 more to pay for the gifts she bought.

Answer 2

the customer will need to pay $68