Answer:
To find out the number coming from each school, you need to use the proportion of the school's population out of the population of all three.
Total population = 618 + 378 + 204
= 1,200 students
North Middle school:
= 618/1,200 * 20
= 10 students
Central Middle School:
= 378 / 1,200 * 20
= 6 students
South Middle School:
= 204/1,200 * 20
= 4 students
