7.8 x 0.35 +0.05 x 7 + 2.1 x 0.35

  =(7,8+2,1+0.05)x 0.35

=9,95 x 0.35

=3.4825

học tốt

7,8 x 0,35 + 0,05 x 7 + 2,1 x 0,35

= 7,8 x 0,35 + 0,35 + 2,1 x 0,35

= 0,35 x ( 7,8 + 1 + 2,1 )

= 0,35 x 10,9

= 3,815

thanks mn nhìu

\(\left(x-\frac{7}{3}\right):2\frac{3}{21}+\frac{3}{5}=0,16\)

<=> \(\left(x-\frac{7}{3}\right):\frac{45}{21}+\frac{3}{5}=\frac{4}{25}\)

<=> \(\left(x-\frac{7}{3}\right):\frac{15}{7}=-\frac{11}{25}\)

<=> \(x-\frac{7}{3}=\frac{-33}{35}\)

<=> \(x=\frac{146}{105}\)

\(\left(x+\frac{5}{6}\right).2\frac{2}{5}-1\frac{1}{4}=0,35\)

<=> \(\left(x+\frac{5}{6}\right).\frac{12}{5}-\frac{5}{4}=\frac{7}{20}\)

<=> \(\left(x+\frac{5}{6}\right).\frac{12}{7}=\frac{8}{5}\)

<=> \(x+\frac{5}{6}=\frac{14}{15}\)

<=> \(x=\frac{1}{10}\)

học tốt

\(\left(\frac{45}{7}-\frac{\frac{3}{4}x-2}{\frac{7}{20}}\right).\frac{14}{5}=10\)

\(\frac{45}{7}-\frac{\frac{3}{4}x-2}{\frac{7}{20}}=\frac{25}{7}\)

\(\frac{\frac{3}{4}x-2}{\frac{7}{20}}=\frac{20}{7}\)

\(\frac{3}{4}x-2=1\)

\(\frac{3}{4}x=3\)

\(x=4\)

Vậy x=4

a)

x= 1/4 - 3/4

x= -1/2

b)

2/3x=1/7 + 3/7

2/3x=4/7

x=4/7:2/3

x=6/7

hok tốt

\(x:\dfrac{3}{4}\) = \(\dfrac{9}{14}-\dfrac{1}{7}\)

\(x:\dfrac{3}{4}\) = \(\dfrac{1}{2}\)

\(x=\dfrac{1}{2}\) x \(\dfrac{3}{4}\)

\(x=\dfrac{3}{8}\)

\(x\)x \(\dfrac{1}{2}-\dfrac{1}{4}\)=\(\dfrac{2}{3}\)

\(x\) x \(\dfrac{1}{4}\)     =\(\dfrac{2}{3}\)

\(x\)            = \(\dfrac{2}{3}:\dfrac{1}{4}\)

\(x\)             \(\dfrac{8}{3}\)

14x - 2 . 7² = 42

14x=140

x=10

ghi rõ cách làm cho mình nha!!!

Bài 1\(57+90-\frac{\Delta y}{\Delta z}\)

\(\Delta=\)

Bài 2\(87+\infty\)

\(\infty=\)

điên hả !?

Thay x

3(0.5-3)(0.5+7)+(0.5-4)²+48

= -641.0625

=\(-\frac{10257}{16}\)

đặt x-1 vào ngoặc bên trong còn (1/3.5+1/5.7+...+1/99.101)=1/303 tới đây là dễ r`

đúng tích nha

\(\Rightarrow\left(x+x+....+x\right)-\left(\frac{1}{3.5}+\frac{1}{5.7}+....+\frac{1}{99.101}\right)=\)\(\frac{1}{303}\)

\(\Rightarrow49x-\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+....+\frac{1}{99}-\frac{1}{101}\right)=\frac{1}{303}\)

\(\Rightarrow49x-\left(\frac{1}{3}-\frac{1}{101}\right)=\frac{1}{303}\)

\(\Rightarrow49x-\frac{88}{303}=\frac{1}{303}\)

\(\Rightarrow49x=\frac{89}{303}\)

\(\Rightarrow x=\frac{89}{303}:49\)

\(\Rightarrow x=\frac{89}{14847}\)

\(-\dfrac{4}{7}-x=\dfrac{3}{5}-2x\\ \Rightarrow-x+2x=\dfrac{3}{5}+\dfrac{4}{7}\\ \Rightarrow x=\dfrac{21}{35}+\dfrac{20}{35}\\ \Rightarrow x=\dfrac{41}{35}\)

Vậy `x=41/35`

__

\(\dfrac{3}{7}x-\dfrac{2}{3}x=\dfrac{10}{21}\\ \Rightarrow\left(\dfrac{3}{7}-\dfrac{2}{3}\right)x=\dfrac{10}{21}\\ \Rightarrow\left(\dfrac{9}{21}-\dfrac{14}{21}\right)x=\dfrac{10}{21}\\ \Rightarrow\dfrac{-5}{21}x=\dfrac{10}{21}\\ \Rightarrow x=\dfrac{10}{21}:\left(-\dfrac{5}{21}\right)\\ \Rightarrow x=-2\)

Vậy `x=-2`

a)

-4/7 - x = 3/5 - 2x

2x - x = 3/5 + 4/7

x = 41/35

Vậy x = 41/35

b)

3/7.x - 2/3.x = 10/21

x(3/7 - 2/3) = 10/21

x.(-5/21) = 10/21

x = 10/21 : (-5/21) = -2

Vậy x = -2