Question

[45 pontos], quanto é :

A) 100x + 80 = 120x - (40x - 300)

B) 50x + 200 = 20 (x - 4) + 100

C) 6x + 3 (10 - 4x) = 25 + 8x

D)19 + 2x - 13 = 10 -20

E) 3x - 10 + 13 = 2x + 28

Answer 1

A) 100x + 80 = 120x - (40x - 300)
      100x + 80 = 120x - 40x + 300
      100x -120x + 40x = 300  - 80
      20x = 220
         x = 11

B) 50x + 200 = 20 (x - 4) + 100
     50x + 200 = 20x - 80 + 100
     50x - 20x = -80 + 100 - 200
     30x = -180
       x = - 6

C) 6x + 3 (10 - 4x) = 25 + 8x
     6x + 30 - 12x = 25 + 8x
     6x - 12x - 8x = 25 - 30
     -14x = 5
            x = -5/14

D)19 + 2x - 13 = 10 -20
     2x = 10 - 20 + 13 - 19
     2x = -16
      x = -8

E) 3x - 10 + 13 = 2x + 28
     3x - 2x = 28 + 10 - 13
     x = 25

Answer 2

a) $100x+80=120x-(40x-300)$

$100x+80=120x-40x+300$

$100x-120x+40x=300-80$

$20x=220~~\Rightarrow~~x=\dfrac{220}{20}~~\Rightarrow~~\boxed{x=11}$.


b) $50x+200=20\cdot(x-4)+100$

$50x+200=20x-80+100$

$50x-20x=100-80-200$

$30x=-180~~\Rightarrow~~x=-\dfrac{180}{30}~~\Rightarrow~~\boxed{x=-6}$.


c) $6x+3\cdot(10-4x)=25+8x$

$6x+30-12x=25+8x~~~~\cdot(-1)$

$-6x-30+12x=-25-8x$

$-6x+12x+8x=-25+30$

$14x=5~~\Rightarrow~~\boxed{x=\dfrac{5}{14}}$.


d) $19+2x-13=10-20$

$2x+6=-10$

$2x=-16~~\Rightarrow~~x=-\dfrac{16}{2}~~\Rightarrow~~\boxed{x=-8}$.


e) $3x-10+13=2x+28$

$3x+3=2x+28$

$3x-2x=28-3~~\Rightarrow~~\boxed{x=25}$.