so first you multiply 8 over 11 and n and you get: 8/11n
then you multiply 8 over 11 and 10 and you get 80 over 11 but then you have to make it a mixed fraction which is 7 1 over 2. then you end up with this equation: 8 over 11n X 7 1 over 2 equals 64. Then im stuck.. because im in 8th grade and in Pre Algebra so im just now learning this.. xD but maybe you can get it from there.