Answer: Soledad used 87 GB in the first six month.
Explanation:
Since we have given that
Amount of space in hard drive of computer = 400 GB
After 6 months,
Amount of space in hard drive of computer = 313 GB
Let the amount of hard drive space she used in first six months be 'x'.
According to question, it becomes,

Hence, Soledad used 87 GB in the first six month.