a) 7 - x =8-(-7)              b) x-8 = (-3)-8 

    7 - x = 15                    x-8 = -11           

         x = 7-15                 x    = -11+8            

         x = -8                     x    = -3

a,7-x=15

x=7-15=-8

b,x-8=-11

x=-11+8=-3

tick minh

7-x=15

x=7-15

x--8

b,x-8=-11

x=-11+8

x=-3

tich minh

a) \(7-x=8-\left(-7\right)\)

\(\Leftrightarrow-x=8+7-7=8\)

\(\Leftrightarrow x=-8\)

Vậy x = - 8

b) \(x-8=\left(-3\right)-8\)

\(\Leftrightarrow x=\left(-3\right)-8+8\)

\(\Leftrightarrow x=-3\)

Vậy x = - 3

a) 7 - x = 8 - (-7)

\(\Rightarrow\) 7 - x = 8 + 7

\(\Rightarrow\) -x = 8

\(\Rightarrow\) x = -8

Vậy: x = -8

b) x - 8 = (-3) - 8

\(\Rightarrow\) x = -3

Vậy: x = -3

\(\dfrac{3}{5}\)\(x\) - \(\dfrac{11}{5}\) = \(\dfrac{-3}{14}\) : \(\dfrac{5}{7}\) 

\(\dfrac{3}{5}\)\(x\) - \(\dfrac{11}{5}\) =  - \(\dfrac{3}{10}\)

\(\dfrac{3}{5}\)\(x\)         = - \(\dfrac{3}{10}\) + \(\dfrac{11}{5}\)

\(\dfrac{3}{5}\)\(x\)       = \(\dfrac{19}{10}\) 

\(x\)         = \(\dfrac{19}{10}\) : \(\dfrac{3}{5}\)

\(x\)        = \(\dfrac{19}{6}\)

\(\dfrac{3}{5}x-\dfrac{11}{5}=-\dfrac{3}{14}:\dfrac{5}{7}\)

\(\Rightarrow\dfrac{3}{5}x-\dfrac{11}{5}=-\dfrac{3}{14}\cdot\dfrac{7}{5}\)

\(\Rightarrow\dfrac{3}{5}x-\dfrac{11}{5}=-\dfrac{3}{10}\)

\(\Rightarrow\dfrac{3}{5}x=-\dfrac{3}{10}+\dfrac{11}{5}\)

\(\Rightarrow\dfrac{3}{5}x=\dfrac{19}{10}\)

\(\Rightarrow x=\dfrac{19}{10}:\dfrac{3}{5}\)

\(\Rightarrow x=\dfrac{19}{6}\)

=> 3x-7+5-x=10

=> 2x-2 = 10

=> 2x = 10+2 = 12

=> x = 12 : 2 = 6

Vậy x = 6

Tk mk nha 

(3x-7)-(-5+x)=10

3x-7+5-x=10

3x-x-7+5=10

2x-2=10

2x=10+2

2x=12x

x=12:2

x+6

Vật x=6

\(\left(3x-7\right)-\left(-5+x\right)=10\)

\(3x-7-5-x=10\)

\(2x=10+12\)

\(2x=22\)

\(x=11\)

vậy \(x=11\)

Ta có: x + 5 < 7 ⇔ x < 7 – 5 ⇔ x < 2

Vậy tập nghiệm của bất phương trình là: {x|x < 2}