(-15)\(x\) = - 45

       \(x\)  = - 45 : (-15)

      \(x\)  = 3

Vậy \(x=3\)

(-15)\(x\) = 10.(-40).(-5)

    -15\(x\)  =  -400.(-5)

   -15\(x\)   = 2000

    \(x\)   = 2000 : (-15)

    \(x\)  = - \(\dfrac{400}{3}\)

Vậy \(x=-\dfrac{400}{3}\) 

(+2).\(x\)  = - 16

      \(x\)   = -16 : (2)

      \(x\)  = - 8

Vậy \(x=-8\)

x+12=40-x-5-15-x

x+12=40-5-15-x-x

x+12=20

x=20-12=8

x+12 = 40- x- 5- 15- x

x+12 = 40 - 5 - 15- x- x

x + 12 = 20

x = 20 - 12

x = 8

x+12 = 40- x- 5- 15- x

x+12 = 40 - 5 - 15- x- x

x + 12 = 20

x = 20 - 12

x = 8

Vậy x = 8

-2x - 40 = (5 - x) - (-15 + 60)

-2x - 40 = (5 - x) - 45

-2x - 40 = -40 - x

-2x - x = 40 - 40

      -3x = 0

         x = 0

2(x - 4) - 3(x + 7) = 14

    2x - 8 - 3x - 21 = 14

                 -x - 29 = 14

                        -x = 14  + 29

                        -x = 43 

                         x = -43

-7(5 - x) - 2(x - 10) = 15

-35 + 7x - 2x + 20 = 15

              -15 + 5x = 15

                       5x = 15 + 15

                       5x = 30

                         x = 6

         \(-2x-40=\left(5-x\right)-\left(-15+60\right)\)

\(\Leftrightarrow\)\(-2x-40=5-x+15-60\)

\(\Leftrightarrow\)\(-2x-40=-x-40\)

\(\Leftrightarrow\)\(-2x+x=40-40\)

\(\Leftrightarrow\)\(x=0\)

Vậy....

\(x+18=2-2x\)

\(2x+x=2-18\)

\(3x=-20\)

\(x=-20:3\)

\(x=\frac{-20}{3}\)

3 x 15 + 21 x 15 + 85 x 5

= 45 + 315 + 425

= 785

15 - 30 + 40 

= 25

21 + 19 - 50 + 10

= 0

\(\dfrac{1}{5}-\dfrac{1}{4}+2\)

\(=-\dfrac{1}{20}+2\)

\(=\dfrac{39}{20}\)

\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)

\(=\dfrac{5}{12}\times\dfrac{1}{4}\)

\(=\dfrac{5}{12}\times\dfrac{3}{12}\)

\(=\dfrac{5}{48}\)

\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)

\(=-\dfrac{9}{20}\)

\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)

\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)

\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)

\(\dfrac{1}{5}-\dfrac{1}{4}+2\)

\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)

\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)

\(=\dfrac{44}{20}-\dfrac{5}{20}\)

\(=\dfrac{39}{20}\)

\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)

\(=\dfrac{5}{12}\times\dfrac{1}{4}\)

\(=\dfrac{5}{48}\)

\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)

\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)

\(=\dfrac{6}{20}-\dfrac{15}{20}\)

\(=-\dfrac{9}{20}\)

Help meeeeeeeeeee

(X+40)x15+(60+x)*5=2000

x*15+40*15+60*5+x*5=2000

x*(15+5)+600+300=2000

x*20+900=2000

x*20=2000-900

x*20=1100

x=1100:20

x=55

-2x-40=(5-x)-(-15+60)

-2x-40=5-x+15-60

-2x+x=15-60+40

      -x=-5

       x=5

Vậy x=5

<=> -2 . x - 40 = 5 - x - 15 - 60 

<=>-2x + x = 5 - 15 - 60 + 40

<=> -x = -30

<=> x = 30

-2.x-40=(5-x)-(-15+60)

<=>-2x-40=(5-x)-45

<=>-2x=5-x-45+40

<=>-2x=-x-10

<=>-x=-10

<=>x=10

Vậy phương trình có No x=10

-2x-40=(5-x)-(-15+60)

=> -2x - 40 = 5 - x + 15 +60

=> -2x - 40 = 80 - x

=> -2x + x = 80 + 40

=> -x = 120

-2x-40=(5-x)-(-15+60)

-2x - 40 = 5 - x - 45

-2x - 40 = -x - 40

-2x + x = -40 + 40

-1x = 0

x = 0