Solution
let the speed ( walk ) = x miles/hr
then the speed ( for run) = 7miles/hr + x miles/ hr
RUN
time = t
distance = 3 miles
speed = distance/ time
(7+x) = 3 / t
t = 3 / (7+x)
WALKS
time = t
distance = 1/2 mile
speed = distance/ time
time = distance/speed
[tex]t=\frac{1}{2x}[/tex]time is the same in both instances
We say t = t
[tex]\begin{gathered} \frac{3}{7+x}=\frac{1}{2x} \\ 6x=7+x \\ 5x=7 \\ x=\frac{7}{5} \\ x=1.4 \\ she\text{ }walks\text{ }at\text{ }1.4miles\text{ }per\text{ }hour \end{gathered}[/tex]