A Simple Math Puzzle

Hey there, it's my first thread that i'm creating so i'm a little bit scared, if i break any rule.

I had one game to give away and i wanted to make it ''Invite only'' so i choose to make a puzzle to make your life harder.

I add an example cause i didn't want to make you waste more than 2 minutes in the puzzle.

You can find the puzzle here (there is more than one possible answers)

The game i'm giving away.

Dont forget to Bump the thread if you solve the puzzle.