Any math experts?

soo tough >< 1 solver :O

Wow, I thought it would take much, much longer! Kudos to the solver!

Interesting puzzle. Will wait for the hint :)

youshallnotcheat ;)

Got only the easy number :/

Got it on my second try. Nice misdirection.

Notice that there are only 1000 possibilities, so with a lot of people trying to solve with many attempts, you easily get many solvers only by chance, without having to know the logic behind.

Solved. Easy puzzle and I'm not first, therefore code is already gone, but thanks anyway.

Saw a similar puzzle just recently.. too bad that there is only one key :( but thanks :)

Okay, here is the solution:

The number behind the = is the sum of closed spaces in the numbers:
1, 2, 3, 5, 7 = 0
4, 6, 9 = 1
8 = 2

The first ? has six spaces and needs to be eight. The only number with two spaces is 8. ;)
The second and third one is simple counting.

I wish it was a giveaway, rather than a steam key.