What is the difference between 400 and the sum of 821 and 77?

The difference between 400 and the sum of 821 and 77 can be calculated by first finding the sum of 821 and 77, which is 898. Then, subtract 898 from 400 to find the difference. Mathematically, this can be represented as 400 - (821 + 77) = 400 - 898 = -498. Therefore, the difference between 400 and the sum of 821 and 77 is -498.