>>>>>>>>Several people answered 40
>>>>>>>>I can get 52 or 96, but not 40.
>>>>>>>>What am I missing?
>>>>>>>
>>>>>>>
>>>>>>>It's easy, Bill
>>>>>>>
>>>>>>>On each row, the number on the right = the sum of two numbers on the left added to the number on the right above
>>>>>>>
>>>>>>>So,
>>>>>>>
>>>>>>>2nd row : 2 + 5 + 5 = 12
>>>>>>>3rd row: 3 + 6 + 12 = 21
>>>>>>>4th row: 8 + 11 + 21 = 40
>>>>>>
>>>>>>Why is 4th row 8+11, rather than 7+10 (Or Marcia's 4+7) ?
>>>>>>I know I am getting old but still do not see it :-)
>>>>>
>>>>>You have to go back to the original message from Bill - and actually click on the picture -
>>>>>Then you will see the 4th row
>>>>
>>>>The 4th row is really the 8th row if you follow the pattern... you're missing 4,5,6,7, so the answer should be 96: 8 + 11 + 77...
>>>
>>>If and only if there is such pattern - and 4, 5, 6 and 7 were not in
>>
>>Yes but the puzzle implies it.... they do this all the time in IQ tests...
>
>That is your interpretation
>
>
>The question was - how do you get to 40 ?

Found this by googling "3 + 6 = 21"... http://www.bhavinionline.com/2016/04/fun-maths-riddle-1-4-5-8-11/
or this: http://www.telegraph.co.uk/education/2016/04/22/this-maths-problem-has-thousands-of-people-baffled-can-you-work/