4/7 was already ate and 100g was remain. for you to get the answer, you must know the fraction form of the remaining ice cream, if 4/7 was ate, automatically the remaining part is 3/7 (this is how to get 7/7 - 4/7)
Now, divide 100 by 3(this is to get 1/7) if you already got the answer(with decimals) multiply it by 7 and that's the answer.

P.S. I gave you the steps not the exact answer for you to know it