Question

64 is 66 2/3 of what number?,

Answer 1

I dont know how to write this mathematically but i'll try-
64 is 66 2/3 of 96
set up the proportion 64 over x = 66 2/3 over 100
cross multiply and youll have 6400 and 66 2/3 x
to find x, divide 6400 by 66 2/3 (aka 200/3)
you should get 96
hope i helped 
(the answer can't be less than 64 since 64 is only part of the whole number)

Answer 2

$64=(66+2/3)x \\ x = 0.96$