If 1 mile is equal to 1.6 km, then our dimensional analysis would be set up like this to solve for m per hour:
. The miles label cancels out leaving us with kkm per hour. Doing that multiplication gives us 12.8 km in one hour. If she can go 12.8 m in one hour, then we multiply that by 2 to find out how far she can go in 2 hours. 12.8*2 = 25.6 km in 2 hours.