Answer:
we know that 120 liked both places and 200 liked Pokhara. To find the number of students that only liked Pokhara 200-120=80 students
we know that 120 liked both places and 220 liked Chitwan. To find the number of students that only liked Chitwan 220-120=100 students
to find number of students that liked neither of places:
add
80+120+100=300. Subtract by total number of students.
350-300=50 students