Answer:
She can swin 3.6 km in 1 hour using freestyle.
Explanation:
If she can swin 0.3 kilometers in 10 minutes or 1/6 hours using backstroke, then her speed on that style is:
If she can swim twice the distance in the same time for freestyle, then her speed on that is twice the one in backstroke. Therefore, her speed on freestyle is:
Since her speed in freestyle is 3.6 km per hour, this means that she can swim a total of 3.6 km in one hour.