8又11/15÷[2又1/3+1又7/9×（4又3/4-1.15）]
=(131/15)÷[7/3+(16/9)×(19/4-23/20)]
=(131/15)÷[7/3+(16/9)×(72/20)]
=(131/15)÷(7/3+32/5)
=(131/15)÷(131/15)
=1