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

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

Find the combined weight of the Cat, Dog and Rabbit in the given picture.

John can place six large boxes or nine small boxes into a carton.

Can you find out in how many cartons can he place sixty-six boxes in total?

Before the start of the car race, John and Jacob have the same amount of fuel in their car. With this fuel, John can drive for 4 hours while Jacob can drive five hours.
After a time they realize that the amount of fuel left in John's car is 1/4th of the fuel in Jacob's.

For how long they are racing?

What's a single-digit number with no value?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

In case you were starting to feel confident, this one was meant for third graders in Vietnam. The answer is 66, but we don't blame you for scratching your head about how they got there.

Replace all '*' with digits 1, 2, 3, 4, 5 and 6 to make below statement true.

* *
x *
=====
* * *

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?