How many protons are in the nucleus of an atom with an atomic number of 15

20 protons

In the given case, the atomic number of the given atom is 15, hence its nucleus contains 15 protons. The number of protons and electrons are the same in atom and that is what keeps it neutral. In the second case, the atomic number is 20. Hence, the atom will contain a total of 20 protons in its nucleus.

is there multiple choice answers?

cytokinesis is the splitting of a cell membrane to form 2 identical daughter cells. it's similar to mitosis as both cells have identical copies of dna and cytokinesis is a step in the mitotic cycle.