Let us assume the common ratio to be = x
Weight of a person on earth = 100 pounds
Then from the given question, we can find that
8x = 100
x = 100/8
= 25/2
= 12.5
Then
The weight of the person in Jupiter = (3 * 12.5) pounds
= 37.5 pounds
So the weight of the person weighing 100 pounds on earth will be 37.5 pounds on Jupiter. I hope this is the answer you were looking for and the procedure is simple enough for you to understand.