The
![i](https://studentforums.biz/cgi-bin/mimetex.cgi?i)
co-ordinates have to be the same in order for something to be due south of something.
Thus, we have to see, how long it takes for the
![i](https://studentforums.biz/cgi-bin/mimetex.cgi?i)
co-ordinates to become equal.
Thus, we got that the speed is
![2i-3.5j](https://studentforums.biz/cgi-bin/mimetex.cgi?2i-3.5j)
So, the
![i](https://studentforums.biz/cgi-bin/mimetex.cgi?i)
co-ordinate of A is
![7](https://studentforums.biz/cgi-bin/mimetex.cgi?7)
.
Thus,
![\frac{7}{2}=3.5](https://studentforums.biz/cgi-bin/mimetex.cgi?\frac{7}{2}=3.5)
The total time to get to the point
![(0,0)](https://studentforums.biz/cgi-bin/mimetex.cgi?(0,0))
is 7 seconds,
![4+3](https://studentforums.biz/cgi-bin/mimetex.cgi?4+3)
.
Thus you simply add the new value to
![7](https://studentforums.biz/cgi-bin/mimetex.cgi?7)
. And you get the answer:
![10.5](https://studentforums.biz/cgi-bin/mimetex.cgi?10.5)