Question 1174525
d=s*t
27=s*t
18=(s-3)*t, since the time for each part is the same
t=27/s
t=18/(s-3)
so 27/s=18/(s-3)
cross-multiply  and 27s-81=18s
9s=81
s=9 mph initially for 3 hours to do 27 miles
s-3=6 mph for 3 hours to do 18 miles