These two questions ask to count the number of cells present in each sample on day 0 and on day 5. To do so, we can consider that cells are those tiny organisms, which are the basic units of life, and that can only be observed through a microscope in most cases. Between their internal structures, it highlights their nucleus for its big size, clearly seen under this optical instrument.
Having this clear, in the pictures, we can see them as rounded structures with a big dot (the nucleus) in the center of them. So we then can count for each of the samples of the first day, four cells, being twelve in total.
For the fifth day, instead, we can see 18, 11, and 10 for the A, B, and C samples, respectively.