Step-by-step explanation:
9mph is 3 times the speed of 3mph. so, she will walk 3 times as long as she was running.
now the question : is walking back part of her 2-hour training, and it all has to fit into that time window ?
or just it that the walking back is already outside of her 2 hours training ?
because then she was running 9mph for 2 hours (9×2 = 18 miles), and had then to walk back these 18 miles with 3mph, which would take 18/3 = 6 hours (as expected 3 times as long as the running).
but if the first case is true, then it is getting interesting.
then she is running x minutes, and is walking back y minutes, where
y = 3x.
and
x + y = 2 hours = 120 minutes.
using the first in the second equation gives us
x + 3x = 2 hours = 120 minutes.
4x = 120 minutes
x = 30 minutes (or half an hour).
and then
y = 3x = 3×30 = 90 minutes.
so, she needs to plan to walk back for 90 minutes or 1.5 hours.
