Solve this guys.

[Banana_Cannon]

You need to explain how you get the answer to get it right.

[Joyman533]

Okay let's take a look at this.
1111 = 0
2222 = 0
5555 = 0
6666 = 4
0000 = 4
So it appears that four 1's, 2's, or 5's results in nothing. However, four 6's and four 0's result in 4.
Each of them has four digits so maybe something in each one counts? Hmm.
Going off of that, let's assume that each 6 and each 0 is worth 1, and each 1, 2, and 5 is worth 0. Let's look at another number that has these digits.
7662 = 2
Each 6 is worth 1, and a 2 is worth 0. Since 1 + 1 = 2, I think the 7 is worth 0 as well.
So here is what we have so far:
1 = 0
2 = 0
5 = 0
6 = 1
7 = 0
0 = 1
We don't know 3, 4, 8, or 9. We need 8 and 9 for the final answer. Let's continue...
9313 = 1
1 is 0, so we are left with 933 = 1
Now, either 9 is 1 or 3 is 0.5. I really don't know which but I'll go with 9 = 1 because it looks less suspicious.
So, I assume 9 = 1.
8096 = 5
0 is 1, 6 is 1, and 9 is 1. Therefore 8 = 2.
Now we have all the definitions necessary.
2 = 0
8 = 2
9 = 1
2889 = 0 + 2 + 2 + 1 = 5

2889 is 5.

[Banana_Cannon]

Congratulations you are right. The reasoning is pretty good but theres something unsolved for. Why are the digits equal to what they are? Theres enough info to figure out why 8 is 2 amd 1 is 0