(1)4ab/3cd×5cd/4ab÷2abc/3d =5ac/bd*3d/2abc =15/2b (2)81-a/a+6a+9÷a-9/a+9×a+3/a-9 =(9+a)(9-a)/(a+3)×(a-9)/(a+9)×(a+3)/(a-9) =(9-a)/(a+3)