Question

Madison leaves her house and bikes north at a
constant speed of 10 miles per hour. If her dad
leaves the same house two hours later, driving
north at a constant speed of 15 miles per hour, how
long will it take him, in hours, to reach Madison?

Answer 1

distanceMad=10*time
distanceDad=15(time-2)
set them equal, solve for time (the time Madison biked). His time is two hours less than that.

Answer 2

d1 = V1 * (2+ t) = Distance Madison traveled.
d2 = V2 * t = Distance dad traveled.
When dad catches up, his distance will be equal to Madison's distance:

d1 = d2.
V1(2+t) = V2*t.
10(2+t) = 15t,
t = ?.