During first semester, the ratio of the number of students in our class to the number of students in gym class was 2 to 7. however, the art classes were really small, and the gym classes with large, so the principal change the students classes for second semester. in second semester, the ratio of the number of students in our class to the number of students in gym class was 5 to 4. if 75 students were in our class second semester, how many were in our class in gym class first semester.