Hi Zahra, I've found a very simple and effective way of calculating percentages. 78% refers to 78 out of every 100, which can also be written as "0.78". Now, we can simply multiply 0.78 by your number (975) to get 760.5 students. Obviously, there isn't a half a student, so we round that number up to 761. So 761 out of 975 students do their homework before 10:00.
I believe the center would be (-4,2) while the radius should be 3.
