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X+ 0,1+X+0,2+...+X+0,5=5,55
<=> 5x X + (0,5+0,1) x 5 :2 = 5,55
<=> 5 x X + 1,5 = 5,55
<=> 5 x X= 5,55- 1,5
<=> 5 x X= 4,05
<=>X= 4,05:5
<=>X=0,81
![](https://rs.olm.vn/images/avt/0.png?1311)
( 11 x 9 - 900 x 0.1- 8) x ( 56.7 x 0.5 + 56.7 x 9.5)
=(99 - 90 - 8) x [56.7(0.5+9.5)]
=1 x [56.7x10]
=1x 567=567
( 11 x 9 - 900 x 0.1- 8) x ( 56.7 x 0.5 + 56.7 x 9.5)
=(99 - 90 - 8) x [56.7(0.5+9.5)]
=1 x [56.7x10]
=1x 567=567
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a.7,15:0,5+7,15.9-7,15=7,15.\left(2+1-1\right)\)
\(=7,15.10=71,5.\)
\(b.3,14:0,1+75\%.3,14+3,14:0,125+81,25.3,14=3,14.\left(10+\frac{3}{4}+8+81,25\right)\)
\(=3,14.100=314.\)
7.15*2+7.15*9-7.15
7.15*(2+9-1)
7.15*10
71.5
b, 3.14*10+7.5*3.14+3.14*8+81.25*3.14
=314*(10+7.5+8+81.25)
=3.14*106.75
=355.195
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2019 x 74+ 2019 x 25 + 2019
2019 x 74 + 2019 x 25 + 2019 x 1
2019 x (74 + 25 + 1)
2019 x 100
= 201900
![](https://rs.olm.vn/images/avt/0.png?1311)
Lời giải:
$x:0,1+x:0,5-x:25\text{%}+x+x=2019$
$x\times 10+x\times 2-x\times 4+x+x=2019$
$x\times (10+2-4+1+1)=2019$
$x\times 10=2019$
$x=2019:10=201,9$
Đáp án A.
![](https://rs.olm.vn/images/avt/0.png?1311)
X : 0,1 - 9,9 = X x 0,1 + 9,9
X x 10 - 9,9 = X x 0,1 + 9,9
10X - 9,9 = 0,1X + 9,9
10X - 0,1X = 9,9 +9,9
9,9X = 19,8
X = 19,8 : 9,9
X = 2
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x:0,1+x:0,5-x:25\%+x+x=2019\)
\(\Rightarrow10x+2x-x:0,25+2x=2019\)
\(\Rightarrow12x-4x+2x=2019\)
\(\Rightarrow10x=2019\)
\(\Rightarrow x=201,9\)
x : 0,1 + x : 0,5 - x : 25 % + x + x = 2019 (dấu chấm lầ dấu nhân)
x . 10 + x . 2 - x : 0,25 + x + x = 2019
x . 10 + x . 2 - x . 4 + x + x = 2019
x . ( 10 + 2 - 4 + 1 + 1 ) = 2019
x . 10 = 2019
x = 2019 : 10
x = 201,9
Vậy x = 201,9