Answer: The haploid number of the organism is 6.
Diploid refers to the state of a cell which contains two copies of chromosomes. In other words, it means a pair of homologous chromosomes is present in the cell.
Haploid refers to the state of a cell which contains only a single set of chromosomes. This means that it is the half of the diploid number as there is no another copy of chromosome present in the cell.
Thus, If an organism's diploid number is 12, its haploid number will be its half, which is 6.