Answer: It is 20
Step-by-step explanation: The reason it is 20 is because it says that there are 15 souvenirs during 3 days. Knowing this factor, you are trying to figure out how many souvenirs are being purchased during one day. To figure that out, you do 15 divided by 3, which gives you 5. Then, for just on extra day, or the fourth day, you just add 5, so the answer is 20.
