20 ÷ 2(5+5)

I do not think that this is correct.  although the presentation is very confusing.

20 ÷ 2(5+5)

=20 ÷ 2*(5+5)

=10*(10)

=100

There is some controversy raging over this one.

I believe that the answer is one, following the order of operations.

20 ÷ 2(5+5)

20/(2*10),  combining 5+5 first, that would give you 10 (still in parenthesis). Since the parenthesis must be operated on first, the 2 must be multiplied next to give 20/20.