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222-9+11+12:2*14+14 = ? ( )

## Toán Lớp 7: Tính a) 11/30+18/35.( 35/54-49/18-28/48) b) ( -23/39).( -13/56).70/23:125/75 Tìm x biết a) (-1/10)+2/5.x+7/10=1/10 b) 1/3+1/2:x=1/5 c

Toán Lớp 7: Tính
a) 11/30+18/35.( 35/54-49/18-28/48)
b) ( -23/39).( -13/56).70/23:125/75
Tìm x biết
a) (-1/10)+2/5.x+7/10=1/10
b) 1/3+1/2:x=1/5
c) (-2/3):x+5/8=1/5

## Comments ( 2 )

1. a) 11/30 + 18/35 . ( 35/54 – 49/18 – 28/48)
= 11/30 + 18/35 . (-287/108)
= 11/30 + (-41/30)
= -1
———————————————–
b) ( -23/39) . (-13/56 ) . 70/23 : 125/75
= 23/168 . 70/23 . 75/125
= 5/12 . 75/125
= 1/4
——————————————
tìm x
a) ( -1/10) + 2/5 . x+ 7/10 = 1/10
(-1/10) + 2/5 . x             = 1/10 – 7/10
(-1/10) + 2/5 . x             = -3/5
2/5 . x            = -3/5 – (-1/10)
2/5 . x            = -1/2
x           = -1/2 : 2/5
x                 = -5/4
————————————————————-
b) 1/3 + 1/2 : x = 1/5
1/2 : x = 1/5 – 1/3
1/2 : x = -2/15
x = 1/2 : (-2/15)
x = -15/4
—————————————————————
c) (-2/3) : x + 5/8 = 1/5
(-2/3) : x            = 1/5 – 5/8
(-2/3) : x                 = -17/40
x                = (-2/3) : (-17/40)
x                      = 80/51

2. Tính
a) 11/30+18/35.( 35/54-49/18-28/48)
=11/30+18/35.(-287/108)
=11/30-41/30
=-1
b) ( -23/39).( -13/56).70/23:125/75
=23/168.42/23
=1/4
Tìm x biết
a) (-1/10)+2/5.x+7/10=1/10
2/5.x+7/10=1/10+1/10
2/5.x+7/10=1/5
2/5.x          =1/5-7/10
2/5.x          =-1/2
x          =-1/2:2/5
x          =-5/4
b) 1/3+1/2:x=1/5
1/2:x=1/5-1/3
1/2:x=-2/15
x=1/2:(-2/15)
x=-15/4
c) (-2/3):x+5/8=1/5
(-2/3):x      =1/5-5/8
(-2/3):x      =-17/40
x       =(-2/3):(-17/40)
x       =80/51