To obtain this answer we need to use the means command to produce the average value of the age variable, in addition to a qualifier, which will restrict the calculation to Africans. To do this, let's type the following command:
means age if race == 1
The above command produces the following table:
Variable | Type Obs Mean [95% Conf. Interval]
-------------+----------------------------------------------------------
age | Arithmetic 4136 23.59043 23.0264 24.15445
| Geometric 4021 16.84792 16.34827 17.36285
| Harmonic 4021 9.246723 8.80783 9.73165
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From the table we can see that the average age of Africans in the sample is roughly 23 years old.