1、(-25/12)÷(-5/3)x4/5
=5/4×4/5
=1
2、(-1 又2/3)÷(-5/3)÷(-0.25)
=1÷（-0.25）
=-4
3、(-3一1又2/1)÷[3又4/3÷(2一3又3/1)x1又5/1]
=(-4又2/1)÷[3又4/3÷(一1又3/1)x1又5/1]
=(-4又2/1)÷[-16/45x1又5/1]
=(-4/9)÷（-8/27）
=3/2
4、(5/6一10/1一15/8)÷(-5/6)
=(5/6一10/1一15/8)×(-6/5)
=-5/6×6/5+10/1×6/5+15/8×6/5
=-1+12/1+9/4
=-36/17