8/9×[3/4-(3/16+1/8)]=8/9×(3/4-5/16)=8/9×(7/16)=7/18
=8/9×(12/16-3/16-2/16)=8/9×7/16=7/18
8/9x[12/16-(3/16+2/16)]=8/9x[12/16-5/16]=8/9x7/16=28/72=7/13