To win the sandwich, you must answer a question related to a variety of subjects. These include literature, math and science. Through April 20, Burger King will post the daily question on their social media channels. To record an answer, you must place an order through the chain's phone app. Solving BK's following question or equation will enable you to gain the promo code. Parental consent is needed for students between the ages of 13 and 17. The promotion is a one-time offer, meaning there is one free Whopper per student.