Respuesta :
The first elevator starts at 6th floor, and it goes up 7 floor twice, so it's going to be 6+2 x 7=6+14=20
The second elevator starts at 20th, it goes down 5 floor 3 times, then goes up 12 floor, so it's going to be 20-3 x 5+12=20-15+12=5+12=17.
20>17 so it's the first elevator.
The second elevator starts at 20th, it goes down 5 floor 3 times, then goes up 12 floor, so it's going to be 20-3 x 5+12=20-15+12=5+12=17.
20>17 so it's the first elevator.