Cite Your Sources!
Whenever someone makes a claim, always ask for their sources. If you want to be technical about it, ask for the publisher’s name, what their credentials are, and whether there are any sources that argue against your opponent’s original claim. In the end, that person will end up debating against themselves.
But if the source is simple mathematics, you know you’re going to have a hard time proving your point. Here’s the problem in question: you need to drive 2,000 miles in a day (24 hours). You’re in a car that travels at 75 MPH, and you don’t need to eat, rest, or sleep. How much does the sun weigh?