To find the unit rate, we just have to divide
[tex]v=\frac{3.5mi}{0.4hr}=8.75mi/hr[/tex]She was going at 8.75 miles per hour.
Then, we use this rate to find the time needed to travel 5 miles.
[tex]\frac{5mi}{8.75mi/hr}=0.57hr[/tex]It will take 0.57 hours to go 5 miles.