You just have to subtract the second time he walked from the first time he walked and you will get... 15. So the percent change is 15 minutes.
With
, we have
![\sqrt{-24}=\sqrt{(-1)(24)}=\sqrt{-1}\sqrt{24}=i\sqrt{24}](https://tex.z-dn.net/?f=%5Csqrt%7B-24%7D%3D%5Csqrt%7B%28-1%29%2824%29%7D%3D%5Csqrt%7B-1%7D%5Csqrt%7B24%7D%3Di%5Csqrt%7B24%7D)
Since
, we can further write this as
![i\sqrt{24}=i\sqrt{2^2\cdot6}=2i\sqrt6](https://tex.z-dn.net/?f=i%5Csqrt%7B24%7D%3Di%5Csqrt%7B2%5E2%5Ccdot6%7D%3D2i%5Csqrt6)
Vertical angle is when opposite angles meet in the middle of two intersecting lines (share the same vertex). They are equal to each other too.
Hope this helps! :)
You would do 120 mins divides by 15 miles = 8
1 mile = 8 mins
6 x 8 = 48 mins