dễ mà

a) -2(2x - 8) + 3(4 - 2x) = -72  - 5(3x - 7)

=> -4x + 18 + 12 - 6x = -72 - 15x + 35

=> -10x + 15x = -37 - 30

=> 5x = -37

=> x = -7,4

b) 3|2x² - 7| = 33

=> |2x² - 7| = 11

=> \(\orbr{\begin{cases}2x^2-7=11\\2x^2-7=-11\end{cases}}\)

=> \(\orbr{\begin{cases}2x^2=18\\2x^2=-4\left(loại\right)\end{cases}}\)

=> \(\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)

tự làm nha !!!

chúc bạn học tốt

\(x+\frac{5}{7}=\frac{7}{8}:\frac{1}{6}\)

\(\Leftrightarrow x+\frac{5}{7}=\frac{21}{4}\)

\(\Leftrightarrow x=\frac{127}{28}\)

\(\frac{72}{104}=\frac{72:8}{104:8}=\frac{9}{13}\)

\(\frac{3}{13}< \frac{4}{13}< \frac{5}{13}< \frac{6}{13}< \frac{7}{13}< \frac{8}{13}< \frac{72}{104}=\frac{9}{13}\)

Tìm x :

a ) \(x+\frac{5}{7}=\frac{7}{8}\div\frac{1}{6}=\frac{7\times6}{8\times1}=\frac{21}{4}\)

\(x=\frac{21}{4}-\frac{5}{7}=\frac{127}{28}\)

b ) \(\frac{15}{6}-x=\frac{5}{8}\times\frac{2}{15}=\frac{1}{12}\)

\(x=\frac{15}{6}-\frac{1}{12}=\frac{29}{12}\)

Rút gọn : \(\frac{72}{104}=\frac{72\div8}{104\div8}=\frac{9}{13}\)

Điền STN thích hợp :

\(\frac{3}{13}< \frac{4}{13}< \frac{5}{13}< \frac{6}{13}< \frac{7}{13}< \frac{8}{13}< \frac{9}{13}\left(\frac{72}{104}\right)\)Những số cần điền là : 4, 5, 6, 7, 8 .

==========> CHÚC HỌC GIỎI  NHỚ K MÌNH <==========

dễ vậy

\(72-\frac{x}{2}=x-\frac{70}{9}\)

\(72-\frac{x}{2}-x+\frac{70}{9}=0.\)

\(\left(72+\frac{70}{9}\right)-\left(\frac{x}{2}+x\right)=0\)

\(\frac{718}{9}-\left(\frac{x}{2}+\frac{x\cdot2}{2}\right)=0\)

\(\frac{718}{9}-\frac{x+\left(x\cdot2\right)}{2}=0\)

\(\frac{x+\left(x\cdot2\right)}{2}=\frac{-718}{9}\)

\(\frac{x\left(1+2\right)}{2}=-\frac{718}{9}\)

\(\frac{x\cdot3}{2}=-\frac{718}{9}\)

\(\frac{x\cdot27}{18}=-\frac{1436}{18}\)

\(\Rightarrow x\cdot27=-1436\)

ok tự tính ko chết vs cái máy mất

a. X  :  1,8  = 72

X             = 72 x 1,8

X             =  129,6

b. 9,3  x 6,7  +  9,3  x 3,3

=  9,3 x ( 6,7 +  3,3 )

=  9,3 x 10 = 93

Ta có : 91-(27+x)=38

       <=>91-27-x=38

       <=>91-27-38=x

       <=>x=26

           39+(x-17)=72

       <=>39+x-17=72

      <=>x=72+17-39

     <=>x=50

Tk mình nha!

\(91-\left(27+x\right)=28\)

\(27+x=91-28\)

\(27+x=63\)

\(x=63-27\)

\(x=36\)

\(39+\left(x-17\right)=72\)

\(x-17=72-39\)

\(x-17=33\)

\(x=33+17\)

\(x=50\)

hok tốt

91 - (27 + x) = 38

91 - 27 + x   = 38

91        + x   = 38 + 27

91        + x   = 65

               x   = 91 - 65

               x   = 26

39 + (x - 17) = 72

39 +  x - 17  = 72

         x - 17  = 72 - 39

         x - 17  = 33

         x          = 33 + 17

         x          = 40

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a/ 2130-(x+130)+72=-64

a/ 2130-(x+130)+72=-64

<=> -x-130+72+2130=-64

<=> x=2130+72-130+64=2136

b/135-|9-x|=35

<=> |9-x|=135-35=100

<=> \(\left[\begin{array}{nghiempt}9-x=100\\9-x=-100\end{array}\right.\)

<=>\(\left[\begin{array}{nghiempt}x=-91\\x=109\end{array}\right.\)

c/10-|x+3|=-4-(-10)

<=> |x+3|=10+4+(-10)

<=>|x+3|=4

<=>\(\left[\begin{array}{nghiempt}x+3=4\\x+3=-4\end{array}\right.\)

<=>\(\left[\begin{array}{nghiempt}x=1\\x=-7\end{array}\right.\)

c/10-|x+3|=-4-(-10)