Khan/khan-exercises — Issue #7838: Properties of numbers 2 - grrrrr....
Author: KhanBugz
Created: 2011-12-05 20:15:00+00:00
State: open
Labels: firefox, hard, win7

it's to hard i don't understand

[properties_of_numbers_2.html?seed=62&problem=addition-identity](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/properties_of_numbers_2.html?seed=62&problem=addition-identity&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/properties_of_numbers_2.html?seed=62&problem=addition-identity&debug&activity=%5B%5D)

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Mozilla/5.0 (Windows NT 6.1; rv:8.0) Gecko/20100101 Firefox/8.0

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