There are 140 respondents with an unidentified relationship to the head of the household. There are several ways to obtain the answer to question 7, one possibility is by using the tabulate command with the missing option. By typing:
tab rel_head, missing
The command above will display a frequency distribution table in the STATA Results window. Using this table, we find the value corresponding to unidentified or "missing" in the table, which is a dot (.) Looking at the "Freq." column, we see that the number of missing values is 140. This means that 140 observations in the data have a value of "." for the variable rel_head.