Let us convert both speeds to meters per minute.
The turtle:
27 km/ hr
1000 m in a kilometer
60 minutes in an hour
(27*1000)/60
= 450 m/min
The girl:
14 dm/ s
0.1 m in a dm
1/60 minutes in a second
(14*0.1)/(1/60)
= 84 m/min
The turtle is
450 - 84
= 366 m/min faster than the girl