You would need to use the distance formula.
Distance = Sqrt((x2-x1)^2+(y2-y1)^2)
Plug in your numbers
Distance = Sqrt((12+4)^2+(12-18)^2)
Distance = 17.09
Hi this message wont send cuz it needs to be 20 characters long :)
The answer is 640 because if you multiply the total student of 6h grade by 100 and divide by 30. You will get the total of student in the school