10除于5/9+1/6X4(要用递等式~)
= 10×9/5+4/6
= 18+2/3
= 18又2/3
7/9除于11/5+2/9X5/11
= 7/9×5/11+2/9×5/11
= （7/9+2/9）×5/11
= 1×5/11
＝5/11
(1/12+1/2-7/12)除于1/7
＝ (1/12+1/2-7/12)×7
= 1/12×7+1/2×7-7/12×7
= 7/12+7/2-49/12
＝3又1/2
（你这题中的-7/12应该是-1/12吧?）