Let's say a person's weight on Earth has a value of 5. It would be 7 on Neptune. We need to figure out what number was multiplied by 5 so that it became 7. To do that, divide 7 by 5 and you get 1.4.
The problem tells us that this one person weighs 150 pounds on Earth. Multiplying that figure by 1.4 will give us 210, and therefore, the person will weigh 210 pounds on Neptune.
