3/4 x 8/9 x 15/16 x ... x 99/100 x 120/121 = 3 x 8 x 15 x 99 x 120/ 4 x 9 x 16 x 100 x 121

= ( 1 x 3 ) x ( 2 x 4 ) x ( 3 x 5 ) x ... x ( 9 x 11 ) x ( 10 x 12 ) / ( 2 x 2 ) x ( 3 x 3 ) x ( 4 x 4 ) x ... x ( 10 x 10 ) x ( 11 x 11 )

= ( 1 x 2 x 3 x ... x 10 ) x ( 3 x 4 x 5 x ... x 12 ) / ( 2 x 3 x ... x 11 ) x ( 2 x 3 x ... x 11 ) = 12/11x2 = 6/11

= 6/11 nha

<=>x.1+x.3/2+x.7/2=252

x.(1+3/2+7/2)=252

x.6=252

x=252:6

=>x=42

a ) X x 6 - 4,99 = 25,01                                               b ) X : 6 = 7/4

     X x 6           = 25,01 + 4,99                                         X : 6 = 1,75

     X x 6           = 30                                                         X      = 1,75 x 6

     X                 = 30 : 6                                                    X      = 10,5

     X                 = 5

a) \(6x-4,99=25,01\)

\(6x=25,01+4,99\)

\(6x=30\)

\(x=5\)

vậy \(x=5\)

b) \(\frac{x}{6}=\frac{7}{4}\)

\(\Rightarrow4x=6.7\)

\(\Rightarrow4x=42\)

\(\Rightarrow x=10,5\)

vậy \(x=10,5\)

\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\cdot\cdot\cdot\cdot\cdot\frac{2016}{2017}\)

\(=\frac{1.2........2016}{2.3.............2017}\)

\(=\frac{1}{2017}\)

a) \(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(x-\frac{1}{4}\right).....\left(1-\frac{1}{2016}\right).\left(1-\frac{1}{2017}\right)\)

\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}......\frac{2015}{2016}.\frac{2016}{2017}=\frac{1}{2017}\)

\(\left(4.5-2\cdot x\right):\frac{3}{4}=1\frac{1}{3}\)

\(\left(4.5-2x\right):\frac{3}{4}=\frac{4}{3}\)

\(\left(4.5-2x\right)=\frac{4}{3}\cdot\frac{3}{4}\)

\(4.5-2x=1\)

\(2x=4.5-1\)

\(2x=3.5\)

\(x=3.5:2\)

\(x=1.75\)

(4,5 - 2 x X) : 3/4 = 1 1/3

(4,5 - 2 x X)         = 1 1/3 x 3/4

(4,5 - 2 x X)         = 1

        2 x X          = 4,5 - 1

        2 x X          = 3,5

              X         = 3,5 : 2

              X         = 1,75

chúc bạn học giỏi ^_^

tk mk nha !!!

\(\frac{2.x}{5}=\frac{24}{2}\)

\(\frac{2.x}{5}=12\)

\(\left(2.x\right):5=12\)

\(2.x=12.5\)

\(2.x=60\)

\(x=60:2\)

\(x=30\)

\(\frac{2\cdot x}{5}=\frac{24}{2}=12=\frac{60}{5}\)

=> 2*x = 60

x = 30

a) Ta có :

\(\frac{7}{12}< \frac{x}{24}< \frac{2}{3}\)

\(\Rightarrow\frac{14}{24}< \frac{x}{24}< \frac{16}{24}\)

\(\Rightarrow14< x< 16\)

\(\Rightarrow x=15\)

Vậy x = 15

b) \(\left(x+1\right)+\left(x+4\right)+\left(x+7\right)+...+\left(x+28\right)=195\)

\(\Rightarrow\left(x+x+x+...+x\right)+\left(1+4+7+...+28\right)=195\)

\(\Rightarrow10x+145=195\)

\(\Rightarrow10x=195-145\)

\(\Rightarrow10x=50\)

\(\Rightarrow x=50:10\)

\(\Rightarrow x=5\)

Vậy x = 5

c) \(\left(x+0,5\right)+\left(x+1,5\right)+\left(x+2,5\right)=33\)

\(\Rightarrow\left(x+x+x\right)+\left(0,5+1,5+2,5\right)=33\)

\(\Rightarrow3x+4,5=33\)

\(\Rightarrow3x=33-4,5\)

\(\Rightarrow3x=28,5\)

\(\Rightarrow x=28,5:3\)

\(\Rightarrow x=9,5\)

Vậy x = 9,5

_Chúc bạn học tốt_

a, \(\frac{7}{12}\)\(< \)\(\frac{x}{24}\)\(< \)\(\frac{2}{3}\)

\(\frac{14}{24}\)\(< \)\(\frac{x}{24}\)\(< \)\(\frac{16}{24}\)

Số lớn hơn 14 và nỏ hơn 16 là : 15

\(\Rightarrow\)Vậy \(x\)= 15

  \(\frac{\left(72\times1995-1996\right)\times\left(18-36\div2\right)\times\left(148\div5-7\right)}{1+3+5+...+1993+1995}\)

= \(\frac{\left(72\times1995-1996\right)\times\left(18-18\right)\times\left(148\div5-7\right)}{1+3+5+...+1993+1995}\)

= \(\frac{\left(72\times1995-1996\right)\times0\times\left(148\div5-7\right)}{1+3+5+...+1993+1995}\)

= \(\frac{0}{1+3+5+...+1993+1995}\)

= 0 : (1 + 3 + 5 + ... + 1993 + 1995)

= 0

(72x1995-1996)x(18-36:2)x(148:5-7) / 1+3+5+....+1993+1995

=(72x1995-1996)x0x(148:5-7) / 1+3+5+...+1993+1995

=0 / 1+3+5+...+1993+1995

=0

Tích nha