Before duplication 1 chromosome = 1 chromatid and after
duplication1 chromosome has 2 chromatids. if a diploid organism had
2n = 12chromosomes, how many chromosomes and chromatids would be
presentin the cell after: a) the first division of meiosis b) the
seconddivision of meiosis c) a mitotic division?

a) the first division of meiosis: 6 chromosomes, 12 chromatids in each cell.

b) the  second division of meiosis: 6 chromosomes, 6 chromatids in each cell.

c) a mitotic division: 12 chromosomes, 12 chromatids in each cell.

Explanation:

Meiosis-I includes separation of homologous chromosomes to the opposite poles during anaphase-I and thereby, reduces the chromosome number to half in each daughter cell. Therefore, after meiosis-I, each daughter cell would have 6 chromosomes and 12 chromatids.  

Meiosis-II includes splitting of centromere and separation of sister chromatids to the opposite poles during anaphase-II. Therefore, after meiosis-II, each daughter cell would have 6 chromosomes and 6 chromatids.  

Mitosis includes splitting of centromere and separation of sister chromatids to the opposite poles during anaphase. Therefore, after mitosis, each daughter cell would have 12 chromosomes and 12 chromatids.  

from the original order (top to bottom) the new order will go

1 (founder)

4 (hawk)

2 (mutate)

3 (next generation)