The ratio of class A to class B is 4:1. If 10 students are transferred from Class A to class B, the ratio of class A to class B will be 7:5, so the ratio of class A to class B will be 7:5

The ratio of class A to class B is 4:1. If 10 students are transferred from Class A to class B, the ratio of class A to class B will be 7:5, so the ratio of class A to class B will be 7:5

If the original number of class B is x, then there are 4x people in class A
If class A transfers 10 people to class B, there will be 4x-10 people in class A and X + 10 people in class B
(4X-10):(X+10)=7:5