Answer: 72 miles.
Step-by-step explanation:
We know the relationship:
Distance = speed*time.
Then we can write the equation for distance as a function of time for Ali as:
A(t) = 12mph*t
where t is time in hours.
Fatimah's equation will be:
F(t) = 18mph*(t - 2h)
where the -2h appears because she starts two hours after Ali.
Fatimah will overtake Ali when F(t) = A(t) (their positions are the same)
Then we need to solve:
12mph*t = 18mph*(t - 2h)
12mph*t = 18mph*t - 18mph*2h
12mph*t = 18mph*t - 36 mi
36 mi = (18mph - 12mph)*t
36mi = 6mph*t
36mi/6mph = t
6h = t
So Ali travels for 6 hours before he gets overtaken, then the total distance that Ali travels is:
A(6h) = 12mph*6h = 72 mi
