For this case we have that the variable "s" represents the number of students in Karla's school. Knowing that at Karla's school there are three times the number of students at the Sandi school (which has 1030 students) we have the following equation:
It would take her 12 minutes because if you mutipy 2/3 by 3/2 then you get 1 (as in one mile) and then you have to do that to the other side too so then you multiply 8 by 2/3 and get 12