A secret lair has a code to only allow members to enter. The person wanting to enter says a random number, then is told a number in response. In order to enter they must say the correct third number. Here are sequences that allowed entrance.
Five because s-e-v-e-n has 5 letters. The first number can be anything, the second number is the number of letters in the first number, and the third number is the number of letters in the second number.
Someone preserving food. The two most common ways of preserving food are canning and freezing. So when you preserve food, if you can can it, you do, otherwise you freeze it.
I’m in an elevator with two other people. When it reaches the first floor, one person gets out and six get in. When it reaches the second floor, three people get out and twelve get in. At the third floor, five leave and nine enter. It rises to the fourth floor, one person gets on and the doors close. Suddenly, the elevator cable snaps and the car smashes to the ground. No one survives the fall, yet I’m alive and know exactly how many people go on and off the elevator at every floor. How is this possible?
Two boys weighing 50 pounds each and their older brother weighing 100 pounds wish to cross a river. Their boat will only hold 100 pounds. How can they all cross the river in the boat?
Alphabet (unfortunately there aren’t any actual dictionary words with every letter in the alphabet, so this gimmicky, somewhat unsatisfying answer has to suffice).