Third of 18000 households is about 6000 households. The number of women in these 18,000 households will depend on the average women per household. The same goes for the number of men per household. The number of children 6-59 is not 6000/3 it is the number of children 6-59 in the third of the households in the survey. You probably need to check the table 2.7 in the final report to get an idea of the number of children in the households surveyed.