Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

How is a fly different from a mosquito?

The teacher told the student that if he told a lie then he will be expelled from school and if he told the truth then he still is expelled from school.

What can a student say to prevent his being expelled from school?

There are 3 apples in the basket and you take away 2. How many apples do you have now?

A boy and his father are caught in a traffic accident, and the father dies. Immediately the boy is rushed to a hospital, suffering from injuries. But the attending surgeon at the hospital, upon seeing the boy, says 'I cannot operate. This boy is my son.' How is this situation explained?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

A blonde put eyeliner on her head. Why?

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'

I have an eye but still cannot see.

Who am I?