Answer:
about 2.565 seconds
Step-by-step explanation:
You want to know the round-trip light time to the moon, which is 384,400 km away, if the speed of light is 299,700 km/s.
Time
The relation between time, speed, and distance is ...
t = d/s
The round-trip distance is twice the one-way distance, so the time is ...
t = (2×384,400 km)/(299,700 km/s) ≈ 2.565 s
It would take about 2.565 seconds for a laser beam to go from the Earth to the moon and back.
