The difference means you need to subtract the smaller value from the larger value. It asks for the difference in grams, but gives you the weight in kilograms. You first need to convert kilograms to grams by multiplying each weight by 1000.
The large adult will weigh 5,000,000 grams.
The small adult will weigh 2,300,000 grams.
Subtract to find answer.
Final answer should be 2,700,000