Answer:
2/5 of the students
Explanation:
Let the total number of students be x. Two-Thirds of the students plan to do some volunteering. Two-Thirds in fraction can be written as 2/3. So the portion of the students which plan to do some volunteering is:

From these students, 3/5 plan to volunteer at community center. So the students who plan to volunteer at community center will be:

This means, among x students, 2/5 of the students plan to volunteer at the community center this summer.