The boy went up at 50, so he took 50* 1=50 steps, and there was no elevator.

The elevator is set to take V steps every second, so the elevator * * * goes up 50*V=50V steps.

The girl left: 60/3=20 20*2=40 steps.

The elevator reaches 60 volts.

50+50V=40+60V, because the elevators have the same length.

The results show that V= 1 elevator moves per second 1 step.

Take the little boy = 50+50 *1= 50+50 =100 steps.

Therefore, the manned surface of the escalator has 100 steps.