In this question, it is given that
You start skiing at an elevation 240 ft from the base of the hill and your elevation decreases 8 ft each minute. Your friend starts skiing 320 ft from the base of the hill and her elevation decreases 12 ft per minute.
Let the elevation is represented by h and time by tminutes .
So we have two equations here, which are
[tex] h = 240-8t, h=320-12t [/tex]
And for same elevation, height is same. THat is
[tex] 240-8t= 320-12t \\ -8t+12t = 320-240 \\ 4t = 80 \\ t= 20 minutes [/tex]
THerefore,after 20 minutes, they are at same elevation .