Answer:

Explanation:

Doubling needs a base of 2, and the original number will need to be multiplied by two.
I don't know how to explain so I'm going to just give an example.
After an hour the original number doubles so 120*2
After two hours: 120*2*2
After 3 hours: 120*2*2*2
2*2 can also be written as

and 2*2*2 can be written as

So the number of hours passed is the exponent, and the base is 2 because the original number is being doubled.