...Is this some trick question?
Statement 8 is incorrect...It claims 2 = 1...
Besides, qeustions not related to math should be considered "off-topic"...
The fallacy is the transition from Step 4 to Step 5
4 (a + b) ( a - b) = b ( a - b)
But if a = b.....then we have
5 (a + b) ( 0) = b ( 0)
So....6 becomes
0 = 0 which is the logical conclusion, not " a + a = a "
If \(a=b=0\), technically 0 + 0 = 0 is correct, and (0+0)(0-0) does equal 0(0-0).