Answer:
6 mph
Step-by-step explanation:
Use formula
[tex]D=r\cdot t,[/tex]
where
D = distance
r = rate
t = time
In your case,
D = 12 mi
Dina:
D = 12 mi
r = 8 mph
t = ?
So,
[tex]12=8t\\ \\t=\dfrac{12}{8}=\dfrac{3}{2}=1.5\ hours[/tex]
Masha:
D = 12 - 3 = 8 mi
r = ?
t = 1.5 hours
Then
[tex]9=1.5r\\ \\r=\dfrac{9}{1.5}=\dfrac{90}{15}=6\ mph[/tex]
