The ratio of soldiers to citizens at the outpost is 3 to 7.
To determine the fraction of people at the outpost who were soldiers, we need to consider the total number of parts in the ratio, which is 3 (for soldiers) + 7 (for citizens) = 10.
The fraction of people who were soldiers can be calculated as the ratio of soldiers to the total number of parts:
3/10
Therefore, 3/10 of the people at the outpost were soldiers.