How many pixel in 50kb?

Answer 1

Image format, bit depth (8, 16, 24, 32...), and color range will impact the file size of an image. Any answer provided based on 50kB alone will be a wild guess.

So, here is a wild guess, 300,000 pixels. It assumes .jpg at 24 bit color depth. This is a very common format and quality used to store digital images.