If you had 25 buttons ( red coloured) and 77 buttons (blue coloured). Half of the blue ones melted due to a supernova in the Atlantic ocean. Multiply red and blue buttons :)
You can round 976 to 1000 and 522 to 500. So it would be 1000 - 500 = 500. The answer you would get after subtracting 976-522 would be more than 400 if you round it.
