Response:
Kayla will manage to achieve the 200 miles distance by biking for 11 days and running for 15 days.
Detailed explanation:
The days Kayla runs will be denoted as x.
The days Kayla rides the bike will be noted as y.
Her running speed is 6 miles per day.
The distance she runs in x days equals 6 miles/day × x.
Her biking speed is 10 miles per day.
The distance she bikes in y days equals 10 miles/day × y.
Kayla's required distance is 200 miles.

With at least 15 days of running, substitute x = 15 days in the earlier equation:



y = 11 days.
Kayla will manage to achieve the 200 miles distance by biking for 11 days and running for 15 days.