Final answer:
The expression representing the amount of money Gregg has is 3x, as he has three times the amount that Danica has, denoted by x.
Step-by-step explanation:
If Danica has x dollars, and Gregg has 3 times the amount that Danica has, then the expression to represent the amount of money Gregg has is 3x. This is because you are taking the amount Danica has (x) and multiplying it by 3 to match Gregg's amount. It's similar to saying 'tripled'. Among the given options, 1) 3x correctly represents what Gregg has.