分數一題...help~

3/5 + (-1又1/4) x 4/5 - (-2/5)
------------------------------------------
1/2 - 3/4 + 2

=0÷7/4

=0

= 3/5 - 1又1/4 x 4/5 + 2/5
--------------------------------------
1/2 - 3/4 + 4/2

=3/5- 5/4 x4/5 + 2/5
------------------------------------
2/4- 3/4 +8/4

=3/5 - 1 +2/5
------------------------
7/8

= 3/5 - 5/5 + 2/5
-------------------------
7/8

= 0
---------
7/8

= 0

答案係 0
分子:3/5+(-5/4)x4/5-2/5=3/5+1-2/5=0
分母:1/2-3/4+2=2/4-3/4+2=(-1/4)+2=1又3/4

先將分子那一部份計好：
0.6 +(-5/4*4/5)+0.4
=0.6-1+0.4
=0

只要分母不是0,答案就必然是0了~

我唔係幾明你e條係咩數~~~ =.="