3/5÷[7/8-(2/5+3/8)]-(4/5-1/4)* 6/11÷9/20
＝3/5÷（7/8-3/8-2/5）-（16/20-5/20）x6/11x20/9
=0.6÷（0.5-0.4）－11/20x6/11x20/9
=0.6÷0.1－6/9
＝6-2/3
＝5又 1/3