There are 53 sons and daughters in the Saldru12 sample. To obtain the answer to question 2, you could have used the following commands:
tab rel_head
The command above will display a frequency distribution table in the STATA Results window. Using this table, we find the value corresponding to resident head in the table, which is 1. Looking at the "Freq." column, we see that the number of sons and daughters is 53. This means that 53 observations in the data have a value of 9 for the variable rel_head.