If the required percentage is 66.67, then you need 8 votes in favor. 7 votes is below 64% and hence insufficient for the supermajority required.

If you have to have AT LEAST 66.67%, then I would say you have to have eight votes to be in compliance with your governing documents and state law.

What part of the English language and math did you fail? 
In the case of an if and only if statement: 
Must be over 2/3 then if and only if the vote count is over 2/3 then the condition (passing) passes.  
Go back to middle school.

Let's keep this respectful John Mastro. You must be a terribly unhappy man as you consistently speak to others in this manner.

Tiny:  
 
John Mastro is usually right, though rarely tactful.  
 
Norman Prigger

Norman, I was not addressing whether he was right or not, I was addressing his bullish disrespect of others. There are many on this site who are new at all this so perhaps if he tried being more instructive with his superior knowledge instead of insulting, he would be more helpful. Have a good day.

If there are 11 members and a two-third vote is required then the correct number is 7 --NOT 8. .667 x 11 = .734 -- .34 is lower than .5; therefore tou round to the lower number or 7. However if the answer was over .5 then you wouls round to the higher number, or 8. 
 
Another thing that needs to be looked at very closely is the exact wording in the docs pertaining to the vote. If it says a two-thirds vote of the members that means two-thirds of 11. However,if it says a two-thirds vote of the members eligible to vote then that means only those members who are not delinquent or in violation of the docs are eligible to vote.

For many associations, the governing documents indicate that votes are conducted by adding up the percentage of ownership of each of the voting units, and not by "one vote per unit". Larger units have a larger percentage of ownership defined in the governing documents, and these units get a higher percentage in any vote. To get the vote total, just add up each unit's percentage (taken from the governing docs).  
 
For my condo association, in the first article of the declaration (Definitions), a percentage of owners is defined in simple terms as the aggregate of unit percentages, irrespective of the total number of owners. If this idea is in your governing docs, then you can forget about dividing and rounding the number of owners, and just add the percentages of ownership. You need to check your governing documents. 

I would edit the oh-so horribly offensive comment, if that was doable. Other blogs have a log in and edit capability. I invite the moderator to alluding to failing English and math, and going back to middle school. 
Of course the answer all depends on the actual definitions in the documents of the numerator and the denominator. 
And yes I am an unhappy man tiny. I am terribly unhappy with the messed up state of affairs of condominium governance, and the laws. I am unhappy with fraud, malfeasance and ignorance. I am unhappy with condominium unit owners that do not bother to educate themselves about their rights and responsibilities. I am unhappy with posters that fail to read the condominium documents before posting questions in ignorance. I am unhappy with attorneys and legislatures for willfully writing laws and contracts in "legalese", and obsolete complex sentence and grammar structures in order to churn business for attorneys.