so she walks 3.5 mph, miles per hour, that's her walking speed rate.
so in 6 hours, she walked
3.5 miles
+ 3.5 miles
+ 3.5 miles
+ 3.5 miles
+ 3.5 miles
+ 3.5 miles
namely 6(3.5) miles in 6 hours.
she did that for 3 weeks, so she did it 3 times, 3 times that much is 6(3.5)+6(3.5)+6(3.5), or 3[ 6(3.5) ].
well, her regular speed is 3.5, so one-half her regular speed will be 3.5/2.
we know she walked one week for 4 hours at half her speed, that means she walked
3.5/2 miles
+ 3.5/2 miles
+ 3.5/2 miles
+ 3.5/2 miles
namely [tex] \bf 4\left[\frac{3.5}{2} \right] [/tex].
[tex] \bf \stackrel{\textit{3 weeks at regular speed for 6 hours}}{3[~~6~(3.5)~~]}~~+~~\stackrel{\textit{one week for 4 hours at half-speed}}{1~~\left[ 4~\left(\frac{3.5}{2} \right) \right]}\\\\\\63~~+~~7\implies 70 [/tex]
