Giúp e với ạ,e cần gấp

Bài 1:
a,5/17 + -15/34 x 2/5
=>5/17-15/34 x 2/5
=>5/17-3/17
=5-3/17
=>2/17
b,1/2 x 5/6 + 2/3 x 75%
=>1/2x5/6+2/3 x 0,75%

=> 1/2 x 5/6 + 1/2
=>5/2x6 + 1/2
=>5+6/12 
=>11/12
c,(-2/5 + 1/3) x (3/2 - 3/7)
=>(-2/-5 + 1/3) x (3/2 - 3/7)
=>-6+5/15 x (3/2 - 3/7)
=>-6+5/15 x21-6/14
=>-1/15 x 15/14
=>-1/-15 x 15/14
=>-1/14 
d,1/5 x 1/10
=> 1/5 x 10
=> 1/50
e,17/8 x 21/16 -5/3 x (1/5 -7/10)
=>-7/-8 x 21/16 - 5/3 x ( 1/5 -7/10)
=> -7x21/-8x16 - 5/3 x (1/5 -7/10)
=> -147/-128 - 5/3 x ( 1/5 -7/10)
=> -147/-128 -1/3 + 7/6
=> -441-128+448/384
=>-121/384
=> -$\frac{121}{384}$
Bài 2:
a,2/3 + ( 5/7 + -2/3)
=>2/3 + 5/7 - 2/3
=>5/7
b,1/5 x 4/7 + 3/7 x 1/5 - 1/5
=> 4/5x7 + 3/7x5 - 1/5
=>4/35 + 3/35 - 1/5
=>(4/35+3/35) - 1/5
=>4+3/35 - 1/5
=>7/35-1/5 
=> 7-7/35
=>0/35
=>0
c,5/13 + -5/7 + -20/41 + 8/13 + -12/41
=>5/13 - 5/7 - 20/41 + 8/13 - 21/41
=>(5/13 + 8/13) -5/7 + (-20/41 - 21 /41)
= 5+8/13 - 5/7 + -20 -21/41
=>13/13 - 5/7 + -41/41 
=> 13/13 - 5/7 -41/41 
=>3731-2665-3731/3731
=>-2665/3731
=>-$\frac{2665}{3731}$
=>5/7
Bài 3:
a,x=-1/4+2/13 
  x=-1/4 + 2/13 
  x= -13+8/52
  x=-5/52
b,x/3=2/3+-1/7
  x/3=2/3-1/7
  x/3=14-3/21
  x/3=11/21
  x=11/21 x 3
  x=11/7
c,-5/6 - x = 7/12 + 280 /3
  -5/6 - x = 7/12 + 280/3
          -x = 7/12 + 280/3+ 5/6
          -x = 7+1120+10/12
          -x =1137/12
           x = -$\frac{1137}{12}$ 
           x = -$\frac{379}{4}$ 
Bài 4:
a,x -  3/10=7/15:3/5
  x - 3/10 = 7/15 x 5/3
  x - 3/10 = 7/3 x 1/3 
  x - 3/10 = 7/3x3
  x - 3/10 = 7/9
  x            = 7/9 +3/10
  x            =     97/90
b,x + 3/22 = 27/121 x 11/9
   x + 3/22 =3/11
   x             = 3/11 - 3/22
   x             =3/22
c,8/23x46/24 =1/3x
  8/23 x 23/23=1/3x
  2 x 1/3         =1/3x
  1/3x             =2x1/3
  x                   =2x1/3 x 3
  x                    =2
d,1/5 : x = 1/5 -1/7
=> Nếu phân số được xác định,mẫu số không thể bằng 0
  x$\neq$ 0
 1/5 : x = 7-5/35
 1/5 : x = 2/35 
 1/5 x 35 =2x
 7 = 2x, x$\neq$ 0
 2x = 7 
 x= 2/7
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