How big is an image that is 8750 kilobytes?

Answer 1

There is no answer to that until you specify the format. Even so if its format includes any compression (jpeg for example) there is no way to get the image size out of the final size since the compression rate depends on image content.

You can guess, that is all. I would guess your are taking about a jpeg from a 12MP camera, still this is nothing but an educated guess.