Semester 1:
let the number of students in the art class be 2a, and the number of the students in the gym class be 7a. (check: the ratio is 2a:7a = 2:7)
so the total number of students is 9a.
semester 2:
the 9a students are go to the art class and gym class at a a ratio of 5: 4,
so 5a students go to the art class, and 4a students go to the gym class.
<span>75 students are in art class in second semester means that 5a=75,
so a=75/5=15.
In the 1st semester the number of students was:
art class: 2a=2*15=30
gym class: 7a=7*15=105</span>
