One tonne is equal to about 2,000lbs. So, if an adult African Elephant weighs 7 tonnes, that is about 14,000lbs. If you subtract 200lbs from 14,000, you get 13,800.
1 tonne = 2,000lbs
7 tonnes * 2,000lbs = 14,000lbs
14,000lbs - 200lbs = 13,800
So your answer would be an adult African Elephant is about 13,800lbs more than a new born elephant.