Answer: she ran 3.53km on the third day.
Explanation:
Let x represent the number of miles that she ran on the second day.
The first day, she ran 1.37 km more than she ran on the second day. This means that the distance that she ran on the first day is
x + 1.37
On the third day, she ran 0.98 km more than the second day. This means that the distance that she ran on the third day is
x + 0.98
The total distance that she wants to run in 3 days is 10km. This means that
x + 1.37 + x + x + 0.98 = 10
3x + 2.35 = 10
3x = 10 - 2.35
3x = 7.65
x = 7.65/3
x = 2.55
The distance that she ran on the third day is
2.55 + 0.98 = 3.53 km