Which of the following uses a variable to represent a person a place or thing that is unknown

Suppose i flip two identical coins. what is the probability that i get one head and one tail?

When 142 is added to a number the result is 64 more then 3 times the number. option 35 37 39 41

The map shows the location of the airport and a warehouse in a city. though not displayed on the map, there is also a factory 112 miles due north of the warehouse. a truck traveled from the warehouse to the airport and then to the factory. what is the total number of miles the truck traveled?