\(\left(100+58\right)\times58+\left(200-42\right)\times12\)

\(=158\times58+158\times12\)

\(=158\times\left(58+12\right)\)

\(=158\times70=11060\)

\(128\times72+14\times256\)

\(=128\times72+14\times2\times128\)

\(=128\times\left(72+28\right)\)

\(=128\times100=12800\)

\(157\times99+123+34\)

\(=157\times99+157\times1\)

\(=157\times\left(99+1\right)\)

\(=157\times100=15700\)

\(67+98\times45+23\)

\(=98\times45+90\)

\(=98\times45+45\times2\)

\(=45\times\left(98+2\right)\)

\(=45\times100=4500\)

13/7-x=13/14

         x= 13/7-13/4

         x=26/14-13/14

          x=13/14

7² - 7 . (13 - x) = 14

49 - 7. (13 - x) = 14

7 . (13 - x) = 49 - 14

7 . (13 - x) = 35

13 - x = 35 : 7

13 - x = 5

x = 13 - 5

x = 8

Chúc bạn học tốt!! ^^

Ta có: \(7^2-7\left(13-x\right)=14\)

\(\Leftrightarrow7\left(13-x\right)=49-14=35\)

\(\Leftrightarrow13-x=5\)

hay x=8

X+\(\dfrac{2}{7}\)=\(\dfrac{1}{2}\)

X     = \(\dfrac{1}{2}\)-\(\dfrac{2}{7}\)
X     = \(\dfrac{3}{14}\)
Chọn đáp án A. \(\dfrac{3}{14}\)

A

1234567890

sai đúng thằng lớp 1

a) x - 5/7 - 13/14 = 1

⇒ x - ( 5/7 + 13/14 ) = 1

    x - 23/14 = 1

    x            = 1 + 23/14

     x          = 37/14

b)

⇒ 3/5 + x+ 6/5 = 11/3

    x + 9/5    = 11/3

     x      = 11/3 - 9/5

     x       = 28/15

Bạn ơi bạn làm đc bao nhiêu thì làm phụ mình nhé 

bài1

a, 

5 - 7 + 3 +(-8)

= -2 + 3 + ( - 8)

=     1    + (-8)= -7

a; - (-5) - (+7) + (+3) + (-8)

  = 5 - 7 + 3  - 8

= (5 + 3 - 8) - 7

= (8 - 8) - 7

= 0 - 7

= - 7

5 + ( x + 27 ) = 64

a) \(\Rightarrow x+27=59\Rightarrow x=32\)

b) \(\Rightarrow x-2=39\Rightarrow x=41\)

c) \(\Rightarrow x+5=-322\Rightarrow x=-327\)

d) \(\Rightarrow5x=35\Rightarrow x=7\)

e) \(\Rightarrow4\left(x-5\right)=56\Rightarrow x-5=14\Rightarrow x=19\)

f) \(\Rightarrow15+x=37\Rightarrow x=22\)

g) \(\Rightarrow7\left(13-x\right)=35\Rightarrow13-x=5\Rightarrow x=8\)

h) \(\Rightarrow10\left(x+1\right)=100\Rightarrow x+1=10\Rightarrow x=9\)