Final answer:
The time at 45 degrees west will be 2 pm.
Step-by-step explanation:
The time at different longitudes can be calculated by considering that the Earth rotates 15 degrees every hour. If the time at 20 degrees west is 4 pm, then at 45 degrees west, which is 25 degrees further west, the time will be 4 pm - (25/15) hours = 2 pm. So, the time at 45 degrees west will be 2 pm.
Learn more about Time zones