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The solution was to check with a color picker each background color and get the RGB values and simply multiply these 3 numbers.

You'd multiply for the first 3 backgrounds and get the numbers shown in the picture doing the same for the 4th one ( where the question mark was) and you'd get the correct answer.

I had do add the math/chemistry/physics items in the background to trick the AIs, otherwise it would have been a fast and easy guess.

Both Gorilla and Adrian1999 were close with it early on, but they probably didn't think to play with the numbers a little and see it's a multiplication.

 9 months ago 

Okay, x3... 🤦‍♀️

I really thought, it was x2 but missed a number and suddenly everything was a mess... 😂