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

Spot 5 differences in two Christmas tree below:

If six children and two dogs were under an umbrella, how come none of them got wet?

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A brand new Mobile Phone was on sale at 20% as a promotional offer. By what per cent must the Mobile price be increased to sell it at the original price again?

Can you find the key in the picture below?

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Through your logical capabilities, can you make 7 an even?