(7 - x) + (10 -x) + (13 - x) + ... + (52 - x) + (55 - x) = 493 
<=>7+10+13+...+55-17x=493 
<=>(55+7).17:2 - 17x=493 
<=>527-17x=493 
<=>x=2

a) \(x+5=20-\left(12-7\right)\)

\(\Rightarrow x+5=20-5\)

\(\Rightarrow x+5=15\)

\(\Rightarrow x=15-5\)

\(\Rightarrow x=10\)

b) \(15-\left(3+2x\right)=2^2\)

\(\Rightarrow3+2x=15-4\)

\(\Rightarrow3+2x=11\)

\(\Rightarrow2x=11-3\)

\(\Rightarrow2x=8\)

\(\Rightarrow x=\dfrac{8}{2}\)

\(\Rightarrow x=4\)

c) \(-11-\left(19-x\right)=50\)

\(\Rightarrow19-x=-11-50\)

\(\Rightarrow19-x=-61\)

\(\Rightarrow x=61+19\)

\(\Rightarrow x=80\)

d) \(159-\left(25-x\right)=43\)

\(\Rightarrow25-x=159-43\)

\(\Rightarrow25-x=116\)

\(\Rightarrow x=25-116\)

\(\Rightarrow x=-91\)

e) \(\left(79-x\right)-43=-\left(17-52\right)\)

\(\Rightarrow\left(79-x\right)-43=52-17\)

\(\Rightarrow79-x-43=35\)

\(\Rightarrow36-x=35\)

\(\Rightarrow x=1\)

f) \(\left(7+x\right)-\left(21-13\right)=32\)

\(\Rightarrow7+x-8=32\)

\(\Rightarrow x-1=32\)

\(\Rightarrow x=32+1\)

\(\Rightarrow x=33\)

g) \(-x+20=-15+8+13\)

\(\Rightarrow-x+20=6\)

\(\Rightarrow x=20-6\)

\(\Rightarrow x=14\)

h) \(-\left(-x+13-142\right)+18=55\)

\(\Rightarrow x-13+142+18=55\)

\(\Rightarrow x+147=55\)

\(\Rightarrow x=55-147\)

\(\Rightarrow x=-92\)

`#040911`

`a)`

\(37 \times 7 - 17 \times 11 + 13 \times 37 + 17 \times 21\)

`= 37 \times (7 + 13) + 17 \times (21 - 11)`

`= 37 \times 20 + 17 \times 10`

`= 10 \times (37 \times 2 + 17)`

`= 10 \times 91`

`= 910`

`b)`

\(5^5 \times 5^2 \div 5^4 - 2^8 \div 2^4\)

`=`\(5^{5+2-4}-2^{8-4}\)

`= 5^3 - 2^4`

`= 125 - 16`

`= 109`

`c)`

\(3^{11}\times12+3^{12}\times5-3^{14}\)

`=`\(3^{11}\times\left(12+3\times5-3^3\right)\)

`=`\(3^{11}\times\left(12+15-27\right)\)

`=`\(3^{11}\times0=0\)

a) = 259 - 187 + 481 + 357

= 910

b) = 5⁷ : 5⁴ - 2⁴

= 5³ - 2⁴ 

= 125 - 16

= 109

Bài 2:

a, 37 x 7 - 17 x 11 + 13 x 37 + 17 x 21

= ( 37 x 7 + 13 x 37) + ( 17 x 21 - 17 x 11)

= 37 x ( 7 + 13) + 17 x ( 21 - 11)

= 37 x 20 + 17 x 10

= 740 + 170

= 910 

b, 5⁵ x 5² : 5⁴ - 2⁸ : 2⁴

= 5⁷: 5⁴ - 2⁴

= 5³ - 16

= 125 - 16

= 109

c, 3¹¹ x 12 + 3¹² x 5 - 3¹⁴

  3¹¹ x ( 12 + 3 x 5 - 13³)

= 3¹¹ x ( 12 + 15 - 3³)

= 3¹¹ x ( 27 - 27)

 = 3¹¹ x 0

= 0 

0,18 x 1230 + 0,9 x 4567 x 2 + 3 x 5310 x 0,6

= 1,8 x 123 + 1,8 x 4567 +1,8 x 5310

= 1,8 x (123 + 4567 + 5310)

= 1,8 x 10000 = 18000

1 + 4 + 7 + 10 + ... + 52 + 55 - 514 

= SSh là : ( 55 - 1 ) : 3 + 1 = 19 ( số ) 

Tổng là : ( 55 + 1 ) x 19 : 2 = 532

= 532 - 514 

= 18

chúc bạn học tốt

493 ⋮ x

⇒ x ∈ Ư(493) = {1; 17; 29; 493}

Mà 10 < x < 100

⇒ x ∈ {17; 29}

Bài 1: Ta có: \(4\dfrac{3}{5}+\dfrac{7}{10}< X< \dfrac{20}{3}\)

\(\dfrac{23}{5}+\dfrac{7}{10}< X< \dfrac{20}{3}\)

\(\dfrac{138}{30}< X< \dfrac{200}{3}\)

\(\Rightarrow X\in\left\{\dfrac{160}{30};\dfrac{161}{30};\dfrac{162}{30};...;\dfrac{198}{30};\dfrac{199}{30}\right\}\)

Bài 2: \(X-2019\dfrac{2}{13}=3\dfrac{7}{26}+4\dfrac{7}{52}\)

\(\Rightarrow X-\dfrac{26249}{13}=\dfrac{85}{26}+\dfrac{215}{52}\)

\(\Rightarrow X-\dfrac{26249}{13}=\dfrac{385}{52}\)

\(\Rightarrow X=\dfrac{105381}{52}\)

Ta có : 493 = 17.29. Vì 0 < x < 100 nên x ∈ {17 ;29}