If 21x = 79x, what is the value of x?

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

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

Who is that with a neck and no head, two arms and no hands? What is it?

Which five letter word can be added at the end of below word to form a
valid word?

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Cristina was born in 1888. She just had her 30th birthday today how did that happen?

Can you replace the question mark with the correct number?

What does this rebus mean?

O
N
C
E
TIME

You need to complete the maze by entering from the entrance marked below in the figure near the yellow circle, bottom left and leaving from the exit point near the green circle, bottom middle.

Rule of Game: You can move only by exchanging green and yellow circles.