Answer
$49.7 \ minutes$
Work Step by Step
First we must convert the speed of $84 miles/hr$ to kilometers/hr. Using the conversion factor $1 mile/hr$ $=$ $1.60934 km/hr$, we can find that $7.5 mi/hr$ $=$ $12.0701 km/hr$ because:
$$7.5 mi/hr\times\frac{1.60934 km/hr}{1 miles/hr} = 12.0701 km/hr$$
Next since we know that time = distance/velocity we can take the distance of 10 km and divide by the velocity or speed of 12.0701 to get a time of roughly $0.82849355 $ hours which is equal to $49.7 minutes$ since $0.82849355 hr \times 60 min = 49.7$
