Compare the numbers by entering < , > , or =.
596.64 596.640
(does not have any answer choices)

Your answer would be:
596.64 = 596.640
Reasoning= If you just take away the zero from 596.640 you would have the same answer as 596.64. Now if you add a zero to 596.64 you still would have the same answer, therefore they are equal.
Hope this helps! (:

She should use 12/3 to measure

Looks pretty good to me!