12-3/5÷2/3=12-3/5×3/2=12-9/10=11又1/1012÷(3/5+2/3)=12÷(9/15+10/15)=12÷19/15=12×15/19=180/1912÷[3/5×(4/3-1)]=12÷(3/5×1/3)=12÷1/5=12×5=60解方程：2/3x÷4/5=3/82/3x=4/5×3/82/3x=3/10x=3/10÷2/...