The question does not ask for the actual percent of the employed out of the 65+s - just whether that percent is greater than 10% or not.
If you can show that the statement allows that percent to be both greater (e.g. 11%) and smaller (e.g. 9%) than 10%, then the statement is insufficient.
If you can show that the statement only allows values greater than 10 for the percent of employed, then the answer to the question "is the percent greater than 10%?" is a definite "yes" and the statement is sufficient.
That's why stat. (2) is sufficient: assuming that the people are either male or female (i.e. no third option), then the percent of employed will be somewhere between 10% and 20%. It can't very well go below 10% - even if the population consists of entirely women, that percent is still 10%, and the more men (with their higher percent employment) you add to the mix, the higher the overall employment rate.
So whatever the percent of employment is, it has to be greater than or equal to 10 - which means that the answer is yes, and the statement is sufficient.
If stat. (2) had used 5% and 15% for female and male, it would've been insufficient, as that would've allowed examples both over and under 10%, depending on the relative weight of the male and female in the population of 65+s.
