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[(6*x-39):3]*28=5628
(6*x-39):3=5628:28
(6*x-39):3=201
6*x-39=201*3
6*x-39=603
6*x=603+39
6*x=642
x=642:6
x=107
( 6x - 72 : 2 - 84) x 28 = 5628
(6x - 36 - 84) = 5628 : 28
6x - 36 - 84 = 201
6x = 201 + (36 + 84)
6x = 321
x = 53,5
a) \(124+\left(118+x\right)=217\)
\(118+x=217-124\)
\(118+x=93\)
\(x=-25\)
vay \(x=-25\)
b) \(\left[\left(6x-72\right):2-84\right].28=5628\)
\(\left(6x-72\right):2-84=5628:28\)
\(\left(6x-72\right):2-84=201\)
\(\left(6x-72\right):2=201+84\)
\(\left(6x-72\right):2=285\)
\(6x-72=285.2\)
\(6x-72=570\)
\(6x=642\)
\(x=107\)
vay \(x-107\)
c) \(71.2-\left(2x+5\right).6=100\)
\(142-\left(2x+5\right).6=100\)
\(\left(2x+5\right).6=142-100\)
\(\left(2x+5\right).6=42\)
\(2x+5=7\)
\(2x=2\)
\(x=1\)
vay \(x=1\)
(6x-72) : 2 - 84 = 5628:28
(6x-72):2-84= 201
(6x -72):2= 201+84
(6x-72):2= 285
6x-72=285x2
6x-72=570
6x= 570+72
6x= 642
x=642:6
x= 107
[ ( 6x - 72 ) : 2 - 84 ] . 28 = 5628
=> ( 6x - 72 ) : 2 = 201
=> 6x - 72 = 402
=> 6x = 474
=> x = 79
A) 1000000 - 107492 : 154 x 28 + 1000
= 1000000 - 19544 + 1000
= 981456
B) 8/15 + 4/7 + 14/30 + 12/21 + 5
= 15/7 + 5
= 50/7
C) 9/13 : 6/11 - 5/12 : 6/11
= 9/13 x 11/6 - 5/12 x 11/6
= (9/13 - 5/12) x 11/6
= 43/156 x 11/6
= 473/936
Bài 2
1) X x2 + X x 1/5 = 8/5
X x (2 + 1/5 ) = 8/5
X x 11/5 = 8/5
X = 8/5 x 5/11
X = 8/11
2) X : 3/8 = 4/3 : 3/6
X : 3/8 = 8/3
X = 8/3 x 3/8
X = 1
a) 1 000 000 - 107 492 : 154 x 28 + 1000
= 1 000 000 - 698 x 28 + 1000
= 1 000 000 - 19544 + 1000
= 980 456 + 1000
= 981 456
b) 8/15 + 4/7 + 14/30 + 12/21 + 5
= ( 8/15 + 14/30 ) + ( 4/7 + 12/21 ) + 5
= ( 16/30 + 14/30 ) + ( 12/21 + 12/21 ) + 5
= 30/30 + 24/21 + 5
= 1 + 24/21 + 5
= ( 1 + 5 ) + 24/21
= 6 + 24/21
= 150/21
= 50/7
\(\frac{7}{8}>\frac{7}{9}>\frac{7}{10}>\frac{7}{11}>\frac{7}{15}\)
Tính :
\(a,\frac{1}{4}+\frac{3}{8}+\frac{5}{16}=\frac{4+6+5}{16}=\frac{15}{16}\)
\(b,\frac{3}{5}-\frac{1}{3}-\frac{1}{6}=\frac{18-10-5}{30}=\frac{3}{30}=\frac{1}{10}\)
\(c,\frac{4}{7}\times\frac{5}{8}\times\frac{7}{12}=\frac{5}{14}\times\frac{7}{12}=\frac{5}{24}\)
\(d,\frac{25}{28}:\frac{15}{14}\times\frac{6}{7}=\frac{25\times14\times6}{28\times15\times7}=\frac{5}{7}\)
Bài làm
a) x - 7 = 5 b) 128 - 3 . ( x + 4 ) = 23
x = 5 + 7 3 . ( x + 4 ) = 128 - 23
x = 12 3 . ( x + 4 ) = 105
Vậy x = 12 x + 4 = 105 : 3
x + 4 = 35
x = 35 - 4
x = 31
Vậy x = 31
c) [ ( 6x - 39 ) : 7 ] . 4 = 12 d) ( x : 3 - 4 ) . 5 = 15
( 6x - 39 ) : 7 = 12 : 4 x : 3 - 4 = 3 ( chỗ này là làm tắt của x : 3 - 4 = 15 : 5 )
( 6x - 39 ) : 7 = 3 x : 3 = 3 + 4
6x - 39 = 3 . 7 x : 3 = 7
6x - 39 = 21 x = 7 . 3
6x = 21 + 39 x = 21
6x = 60 Vậy x = 21
x = 60 : 6
x = 10
Vậy x = 10
# Chúc bạn học tốt #
x - 7 = -5
x = -5 + 7
x = 2
Vậy x = 2
128 - 3.( x + 4 ) = 23
3.( x + 4 ) = 128 - 23
3.( x + 4 ) = 105
x + 4 = 105 : 3
x + 4 = 35
x = 35 - 4
x = 31
Vậy x = 31
[ ( 6x - 39 ) : 7 ] . 4 = 12
[ ( 6x - 39 ) : 7 ] = 12 : 4
[ ( 6x - 39 ) : 7 ] = 3
( 6x - 39 ) : 7 = 3
6x - 39 = 3 x 7
6x - 39 = 21
6x = 21 + 39
6x = 60
x = 10
Vậy x = 10
( x : 3 - 4 ) . 5 = 15
x : 3 - 4 = 15 : 5
x : 3 - 4 = 3
x : 3 = 3 + 4
x : 3 = 7
x = 21
Vậy x = 21
a) (x.7 +8):5=10
x.7 +8= 10.5=50
x.7= 50-8=42
x= 42:7=6
b) 280: (7+3.x)=4
7+3.x= 4.280= 1120
3.x= 1120-7 =1113
x= 1113: 3= 371
c) (x.5) .19:13= 57
(x.5). 19= 57.13= 741
x.5= 741: 19= 39
x= 39:5 =7,8
d) 6.(28-8).x = 72
20.x= 72:6= 12
x= 12: 20= 0,6
e) 4. (36-4.x)= 3,2
36-4.x= 32:4= 0,8
-4.x= 0,8- 36= -35,2
x= -35,2 : -4 = 8,8
f) (x-15).3 :12= 6
(x-15).3 = 6. 12= 72
x-15= 72: 3= 24
x= 24+ 15= 39
g) (x:4+ 6) . 7 = 70
x:4+6= 70:7= 10
x:4= 10-6= 4
x= 4.4 = 16
h) (x:2+50) :5= 12
x:2+ 50= 12.5= 60
x:2= 60-50= 10
x= 10.2=20
l) 5.(7+3.x)= 140
7+3.x= 140:5 = 28
3.x= 28-7 =21
x= 21: 3= 7
k cho mình nhe
x - 7 = -5
x = -5 + 7
x = 2
|x| = 3
=> x = 3 hoặc x = -3
bạn coi lại đề nha
8 - x = 12
x = 8 - 12
x = -4
6x - 39 = 5628 : 28
6x - 39 = 201
6x = 201 + 39
6x = 240
x = 240 : 6
x = 40
1) x-7=-5
x= -5 +7
x=2
3) /x/=3
=>x= -3 hoặc x=3
câu 3 sai đề
4) 8-x=12
x=8-12
x= -4
5) 6x-39=5628:28
6x-39=201
6x=201+39=240
x=240:6
x=40