a)2x+3=5-x

   2x+x=5-3

   3x    =2

     x    =2/3

b)2x(x-3)=30+x(2x-5)

  2x^2-6x=30+2x^2-5x

  2x^2-6x-2x^2+5x=30

  -x                            =-30

c)2x+2(x+5)=150

   2x+2x+10=150

   4x              =140

    x               =35

d)3x+5(x-10)=1310

   3x+5x-50=1310

   8x             =1360

     x             =170

e)1,5x+2,4(x-100)=2100

   1,5x+2,4x-240 =2100

    3,9x                  =2340

         x                   =600

g)x/3 - x/12 = 3/4

   4x/12 - x/12 = 9/12

   3x/12             =9/12

       3x              =9

         x              =3

h)x/36 +1/2 +x/45 =5

   5x/180 + 90/180 +4x/180 = 900/180

   5x +90 +4x =900

   9x                 =810

     x                  =90

Chúc học tốt !

Bài 1

a, 2x + 3 = 5 - x

<=> 2x + x = 5- 3

<=> 3x = 2 

<=>  x = $\frac{2}{3}$ 

b, 2x (x -3) = 30 + x(2x-5)

<=>  $2x^{2}$ - 6x = 30 + $2x^{2}$ -5x 

<=>  $2x^{2}$ - $2x^{2}$ -6x + 5x = 30

<=> -x = 30

<=> x = -30 

c , 2x  + 2(x+5)= 150

<=> 2x + 2x + 10 = 150

<=> 4x = 140

<=> x = 35

d , 3x + 5(x-10) = 1310

<=> 3x + 5x -50 = 1310

<=> 8x = 1360

<=> x  = 170 

e, 1,5x + 2,4(x-100) = 2100

<=> 1,5x + 2,4 x - 240 = 2100

<=> 3,9x = 2340 

<=> x = 600

f, $\frac{x}{36}$ - $\frac{x}{45}$ = $\frac{2}{3}$

<=> $\frac{5x}{180}$ - $\frac{4x}{180}$ = $\frac{120}{180}$

==> 5x - 4x =120

<=> x = 120 

g, $\frac{x}{3}$ - $\frac{x}{12}$ = $\frac{3}{4}$ 

<=>$\frac{4x}{12}$ - $\frac{x}{12}$ = $\frac{9}{12}$ 

==> 4x - x =9 

<=> 3x = 9

<=> x =3 

h, $\frac{x}{36}$ + $\frac{1}{2}$ + $\frac{x}{45}$ = 5 

<=> $\frac{5x}{180}$ + $\frac{90}{180}$ + $\frac{4x}{180}$ = $\frac{900}{180}$ 

==> 5x + 90 + 4x = 900

<=> 9x = 810

<=> x = 90