Santiago's bill for lunch at a restaurant was $79.40. He left a 20% tip. What was the amount of the tip?

79.40*.2 = $15.88

Step-by-step explanation:

You are permitted to give up to $13,000 each year to any individual without acquiring gift tax liability. So, Barry and Mary each can gift $13,000 to anyone of their choosing. For eight recipients (3 children and 5 grandchildren), each can gift $104,000. Consequently, Barry and Mary can offer $208,000 ($104,000 x 2) to their children and grandchildren in 2013.