a) \(\frac{29}{30}\)- (\(\frac{13}{23}\)+X)=\(\frac{7}{69}\)

\(\frac{13}{23}\)+X=\(\frac{29}{30}\)-\(\frac{7}{69}\)

\(\frac{13}{23}\)+X=\(\frac{199}{230}\)

X=\(\frac{199}{230}\)-\(\frac{13}{23}\)

X=\(\frac{3}{10}\)

b)1/2+1/6+1/12+...+1/x(x+1)=2011/2012

=>1/1.2+1/2.3+1/3.4+...+1/x(x+1)=2011/2012

=>1-1/2+1/2-1/3+1/3+1/4+...+1/x+1/x+1=2011/2012

=>1-1/x+1=2011/2012

=>1/x+1=1-2011-2012

=>1/x+1=2012/2012-2011/2012

1/x+1=1/2012

=>x+1=2012

=>x=2011

a) 3/10

a) \(x+\frac{7}{12}=\frac{17}{18}-\frac{1}{9}\)

\(\Rightarrow x+\frac{7}{12}=\frac{5}{6}\)

\(\Rightarrow x=\frac{5}{6}-\frac{7}{12}\)

\(\Rightarrow x=\frac{1}{4}\)

b) \(\frac{29}{30}-\left(\frac{13}{23}+x\right)=\frac{7}{69}\)

\(\Rightarrow\frac{13}{23}+x=\frac{29}{30}-\frac{7}{69}\)

\(\Rightarrow\frac{13}{23}+x=\frac{199}{230}\)

\(\Rightarrow x=\frac{199}{230}-\frac{13}{23}\)

\(\Rightarrow x=\frac{3}{10}\)

a)\(x+\frac{7}{12}=\frac{17}{18}-\frac{1}{9}\)

\(x+\frac{7}{12}=\frac{5}{6}\)

\(x=\frac{5}{6}-\frac{7}{12}\)

\(x=\frac{1}{4}\)

b)\(\frac{29}{30}-\left(\frac{13}{23}+x\right)=\frac{7}{69}\)

\(\left(\frac{13}{23}+x\right)=\frac{29}{30}-\frac{7}{69}\)

\(\left(\frac{13}{23}+x\right)=\frac{199}{230}\)\(x=\frac{199}{230}-\frac{13}{23}\)

\(x=\frac{3}{10}\)

Tìm x biết:

\(\frac{x}{3}-\frac{3}{4}=\frac{1}{12}\)

\(\frac{x}{3}=\frac{1}{12}+\frac{3}{4}\)

\(\frac{x}{3}=\frac{5}{6}\)

\(x=\frac{5}{6}.3\)

\(x=\frac{5}{2}\)

Vậy \(x=\frac{5}{2}\)

\(\frac{29}{30}-\left(\frac{13}{23}+x\right)=\frac{7}{69}\)

\(\frac{13}{23}+x=\frac{29}{30}-\frac{7}{69}\)

\(\frac{13}{23}+x=\frac{199}{230}\)

\(x=\frac{199}{230}-\frac{13}{23}\)

\(x=\frac{3}{10}\)

Vậy \(x=\frac{3}{10}\)

Bài 2: tính

\(\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}\)

\(=\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}\)

\(=\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}\)

\(=\frac{1}{5}-\frac{1}{11}\)

\(=\frac{6}{55}\)

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)

\(=\frac{1}{1}-\frac{1}{50}\)

\(=\frac{49}{50}\)

Bài 2:

1/30+1/42+1/56+1/72+1/90+1/110

=1/5.6+1/6.7+1/7.8+1/8.9+1/9.10+1/10.11

=1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11

=1/5-1/11=6/55

b)1/1.2+1/2.3+...+1/49.50

=1-1/2+1/2-1/3+...+1/49-1/50

=1-1/50

=49/50

a x=1/4                                                       b x= 3/10

làm chi tiết k bn?

Bài1

a) 25/42 - 20/63 =5/18

b) 9/50 - 13/75 - 1/6 = -4/25

c) 2/15 - 2/65 - 4/39 = 0

Bài2

a)  x + 7/12 =17/18-1/9                       b) 29/30 - (18/23 + x)=7/69

     x + 7/12 = 5/6                                                       18/23 + x =29/30 - 7/69

     x              =5/6 - 7/12                                              18/23 +x = 199/230

     x              = 1/4                                                                      x = 199/230 - 18/23

                                                                                                    x= 19/230

1

x + 7/12= 15/18

x= 15/18-7/12

x= 1/4

k mk nhé

3

4/10= 2/5

\(\frac{x}{15}\)=\(\frac{2}{5}\)

x= 15:5x2= 6

x= 6

k mk nhé

13/23+x=29/30-7/69

13/23+x=199/230

x=199/230-13/23

x=3/10

\(\dfrac{29}{30}-\left(\dfrac{13}{23}+x\right)=\dfrac{7}{69}\)

\(\dfrac{13}{23}+x=\dfrac{29}{30}-\dfrac{7}{69}\)

\(\dfrac{13}{23}+x=\dfrac{2001}{2070}-\dfrac{210}{2070}\)

\(\dfrac{13}{23}+x=\dfrac{1791}{2070}\)

\(x=\dfrac{1791}{2070}-\dfrac{13}{23}\)

\(x=\dfrac{1791}{2070}-\dfrac{1170}{2070}\)

\(x=\dfrac{621}{2070}=\dfrac{3}{10}\)

a: x/5=32/80

nên x/5=2/5

hay x=2

13/x=26/30

nên 13/x=13/15

hay x=15

-x/7=22/-77

=>x/7=2/7

hay x=2

b: x/9=28/36

=>x/9=7/9

hay x=7

-10/x=50/55

=>-10/x=10/11

hay x=-11

a)

1) x/5 = 32/80

\(x : 5 = 32 : 80\) \(x = 5 \cdot \frac{32}{80}\) \(x = 5 \cdot \frac{2}{5}\) \(x = 2\)

2) 13/x = 26/30

\(13 : x = 26 : 30\) \(13 \cdot 30 = x \cdot 26\) \(390 = 26 x\) \(x = 390 : 26\) \(x = 15\)

3) -x/7 = 22/(-77)

\(- x : 7 = 22 : \left(\right. - 77 \left.\right)\) \(- x = 7 \cdot \frac{22}{- 77}\) \(- x = 7 \cdot \left(\right. - \frac{2}{7} \left.\right)\) \(- x = - 2\) \(x = 2\)

b)

1) x/9 = 28/36

\(x : 9 = 28 : 36\) \(x = 9 \cdot \frac{28}{36}\) \(x = 9 \cdot \frac{7}{9}\) \(x = 7\)

2) -10/x = 50/55

\(- 10 : x = 50 : 55\) \(- 10 \cdot 55 = 50 x\) \(- 550 = 50 x\) \(x = - 550 : 50\) \(x = - 11\)

3) 23/(-x) = 46/50

\(23 : \left(\right. - x \left.\right) = 46 : 50\) \(23 \cdot 50 = 46 \left(\right. - x \left.\right)\) \(1150 = - 46 x\) \(x = 1150 : \left(\right. - 46 \left.\right)\) \(x = - 25\)

✅ Kết quả cuối cùng

a)

1. x = 2
2. x = 15
3. x = 2

b)

1. x = 7
2. x = -11
3. x = -25