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

You have to fill the below given grid in a manner that every row and column contains the digits 1 to 6. Also, make sure that the squares that are connected with each other must contains the same digit.

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If EELS + MARK + BEST + WARY = EASY

What does HELP + BARK + WARD + LEAD equal?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

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What is the minimum number of boxes you must check in order to label all boxes correctly?