X is how many channels are correctly selected; The test paper consists of 25 multiple-choice questions, which are not selected or wrongly selected as (25-x).

"Do you understand? The following are the assumptions of the equation.

If you choose the right question, you will get 4 points, and if you choose the right question, you will get 4x.

Deduct 1 point for not choosing or choosing the wrong question, and the deduction will be (25-x)* 1, abbreviated as (25-x);

So according to the meaning of the question, the equation is 4x-(25-x)=85.

Then remove the brackets of 4x-25+x=85.

That is 5x=85+25.

That is 5x= 1 10.

(This formula shows that 5 times x equals 1 10, so x equals110 divided by 5).

x= 1 10/5=22