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 find out the remainder when 3^300 is divided by 5?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

Solve below popular number sequence
314 159 265 358 979 323 846 ?

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How do you go from 98 to 720 using just one letter?

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