If a parent cell has 24 chromosomes how many does each daughter cell have?

The answer to your question depends on whether cells are dividing after mitosis or meiosis.  I will give explanations for both.

During mitosis, the nuclear content of the cells divides just prior to cytokinesis when the cell itself divides.  Prior to mitosis, the DNA contained in the parent cell is duplicated.  This happens during the S (synthesis) phase of interphase.  When mitosis starts the cell still has 24 chromosomes, but there is an extra copy of each.  You can see these as each chromosome, once condensed, appears as an "X".  Each side of the X, is a sister chromatid.  Sister chromatids are exact copies of each other.  

During the process of mitosis the nuclear envelope disappears, chromosomes condense, line up along the metaphase plate, sister chromatids are pulled to opposite sides of the cell, and the nuclear envelope reforms.  After mitosis, the cell splits by cytokinesis.  Because the nuclear content had been copied prior to mitosis, the combination of mitosis and cytokinesis results in 2 identical daughter cells.  After mitosis, the daughter cells would still each have 24 chromosomes.

Nuclear content is also copied prior to meiosis, but the ultimate goal of meiosis is to create sex cells (eggs and sperm) so two rounds of meiosis occur in order to reduce the nuclear content by the end of the process.  During the first round, meiosis I, the nuclear envelope disappears, chromosomes condense and exchange homologous content, homologous chromosomes pair and line up at the metaphase plate, homologous chromosomes are pulled to opposite poles of the cell, the nuclear envelope reforms, and then cytokinesis occurs.  During meiosis II the process is very similar to mitosis.  The nuclear envelope disappears, chromosomes condense, chromosomes line up along the metaphase plate, sister chromatids are pulled to opposite sides of the cell, and the nuclear envelope reforms.  Cytokinesis follows in both daughter cells resulting after meiosis I.  

Because there are two rounds of division without duplication in between, the genetic content is cut in half.  Each of the 4 daughter cells will only end up with half of the genetic content of the parent cell.  Therefore, after meiosis, the daughter cells would have only 12 chromosomes each.  This makes sense because as sex cells they can combine with the sex cell of the opposite sex (each having 12 chromosomes) to create a zygote which would again have the 24 chromosomes.