I have a couple of ideas, but they are both long shots:
number 7, so it says 2 1 2 = 5. There are no symbols though so there is a lot of assumption involved
Or number 12, and move it between 15 and 18 so it reads 2 + 7 = 9. It's not a traditional 7 but it kind of looks like a 7
There is a way with a clear solution. Your second way is a good idea, but for this kind of riddles all numbers are displayed like a digital clock
Yep, got it. It seems so obvious now...
Move 4 to the other side, so it is still between 3 and 5. So now it should read:
3 +2 = 5
correct :)
Woww it's so easyonce you know what the answer is