Ms. Hernandez takes 56 students to the museum. Some of the students travel in a van and some travel on a bus. Going to the museum, the ratio of students in the van to students on the bus is 2 : 5 Going back to school, 2 students move from the van to the bus.​

I think we are missing part of the question.

But if it's looking for how many students rode the bus and van on the way to the museum when the ratio was 2:5, it's 16 students in the van and 40 students in the bus.

On the way home, it was 14 students in the van and 42 students in the bus,   the ratio changes to 1:3