I'm so glad you posted this. That page blew my mind. And not because of
the "equation" itself. But the mass amounts of people who thought they
were right when they were not. It was intriguing. There's no special way
to get the right answer; what's right, is right. First off– only add
when it says "add". This is where people's brains stopped digging (if
they ever even started in the first place). So, given that::::

Start with— 1000.
ADD 40.
ADD 1000.
ADD 30.

Skip– "again 1000"(makes no sense, literally, think about it).

Continue with— ADD 20.

SKIP– "add AGAIN 1000"(The people whose answers were 3090 failed to see that it makes no sense either).

skip– "and finally" 10.

Outcome: 1000+40+1000+30+20 = Answer: 2090.

((((For the ones saying the periods ended one equation and started
another.. the periods should not exist there in the first place. This is
NOT a sentence– it is an equation. You have you (+) for ADDing (the
plus signs are the only things that could possibly contribute to the
EQUATION– and that's it. If anything, the (.) could be labeled
decimals. And if you were to argue that they WERE periods, there is no
rule in the 'math rule book' that would claim that a PERIOD would
separate two equations in a word/equation problem. If there is, let me
know!)))).

Basically
what this came down to was fail English(most likely not on purpose).
So, though it seems like people are thinking about it to hard– a lot of
it was improper so people who had some reading capabilities took it as a
technical challenge, which would make the technical answer the right
answer..technically.

The answer is ————–2090.————————–
All you 4100's and 5000's are simply wrong. Good day..