Starting at home, emily traveled uphill to the hardware store for 60 minutes at just 6 mph. she then traveled back home along the same path downhill at a speed of 12mph. what is her average speed for the entire trip from home to the hardware store and back?

At a 6mph speed, it took Emily 60m

If she returns at a speed of 12mph, it'll take half the time so 30m.

The total of time she took to travel is
30m+60m=90m

the 6mph part represents 2/3 of the time
and the 12mph part reprensents 1/3 of the time

So then
(2/3•6)+(1/3•12)=8

So Emily has an average of 8mph for the entire ride