I am also confused by boolean 3:
If 10/3 <= 10/2 (which it is!) then that is True, so the not would make the answer “False”, I have clearly misunderstood some fundamental early on, I think!

Boolean 3 evaluates the comparison of the remainders of two divisions, not the quotient. Thus, the remainder of 10/3 (which is 1) is > the remainder of 10/2 (which is 0). Hence, the expression evaluates to False, and not 1 <= 0 is True.

If you simplify the equation, not “not false”, “not false” becomes true. So now it reads “not true” which we know is now False. So boolean 5 = False. The nots essentially cancel each other out.

Your problem is that ** (two asterisks rather than one) does not mean multiplication, it means raise the number to a higher power. 3 ** 2 is three squared, for example. Bearing that in mind, the process for solving the problem you posted should be fixed to this:
not 3 ** 2 + 4 ** 2 != 5**2
not 9 + 16 != 25
not 25 != 25
not False
True