First find the number of students in Mr. Feldstein's class who prefer goldfish: 2/3 * 30 students = <<2/3*30=20>>20 students
Then find the number of students in Mr. Feldstein's class who prefer goldfish: 1/6 * 30 students = <<1/6*30=5>>5 students
Then find the number of students in Ms. Henderson's class who prefer goldfish: 1/5 * 30 students = <<1/5*30=6>>6 students
Then add the number of students from each class who prefer goldfish to find the total: 20 students + 5 students + 6 students = <<20+5+6=31>>31 students
#### 31