Since we can see that every digits if some up do not get into 10, we can add from the right.
3 + 2 = 5
6 + 3 = 9
8 + 1 = 9
So the answer is 599
Second way:
round down the digits into hundreds, tens, and ones then get the sum of those.
300 + 200 = 500
60 + 30 = 90
8 + 1 = 9
500 + 90 + 9 is 599
