2/25=.2../25                                                                                                               .27../36=3/4                                         

3/.12..=9/36

15/27=5/..9.. 

..20..28=5/7

36/72=..1../2

\(\dfrac{2}{25}=\dfrac{2}{25}\)
\(\dfrac{27}{36}=\dfrac{3}{4}\)
\(\dfrac{3}{12}=\dfrac{9}{36}\)
\(\dfrac{15}{27}=\dfrac{5}{9}\)
\(\dfrac{20}{28}=\dfrac{5}{7}\)
\(\dfrac{36}{72}=\dfrac{1}{2}\)

TK
2/25=.2../25
27../36=3/4                                        
3/.12..=9/36

15/27=5/..9.. 

..20..28=5/7

36/72=..1../2

a) -72.17+72.31 - 36 . 228

 = -72.17 + 72. 31 - 36.2.114

 = -72 .17 + 72 . 31 -72 . 114

 = -72. ( 17-31+114)

 = -72 . 100

 = -7200

b) ..........

 = -7 . ( 16-36.9) -(-125) 

 = -7 . ( 16-324) +125

 =-7 . ( -308) +125

 = 2156+125

 = 2281

$a)$

$-72.17+72.31-36.228$

$=-72.17+72.31-36.2.114$

$=-72.17+72.31-72.114$

$=72(31-17-114)$

$=72.(-100)=-7200$

$b)$$-7.[{(-2)}^4+(-36):(-3^2)]-{(-5)}^3$

$=-7.[16-36:(-9)]+125$

$=-7.[16--4]+125$

$=-7.20+125$

$=-140+125$

$=-15$

$c)$$(57-725)-(605-53)$

$=57-725-605+53$

$=(57+53)-120$

$=110-120=-10$

$a)$

$-72.17+72.31-36.228$

$=-72.17+72.31-36.2.114$

$=-72.17+72.31-72.114$

$=72(31-17-114)$

$=72.(-100)=-7200$

x-72:36=18

x-2=18

x=18+2

x=20

1, x-72:36=18

x-2=18

=> x=20

2, \(\dfrac{x}{3}-\dfrac{1}{4}=\dfrac{-5}{6}\)

\(\dfrac{x}{3}=\dfrac{-7}{12}\)

12x= -21

->x= \(\dfrac{-21}{12}\)

x/3-1/4=-5/6

x/3=-5/6+1/4

x/3=-7/12

x=-7/12.3

x=-7/4

Cách ghép đúng là: 1 - D; 2 - B; 3 – C ; 4 - A

Mình ghi kết quả thôi nhé!

a.2/3

b.1/3

c.3/2

d.18

e.21

f.6/5

g.53/60

h.-13/18

           giải

a) 1/3 +1/4 +1/12 = 2/3

b) 3/9 + 12/39 - 1/3  = 1/3

c) 72/36 - 1/2 = 3/2

d) 34 - 32 và 1/2 = 18

e) 68/2 - 52/4 = 21

g) 1/2 + 1/3 + 1/4 - 1/5 = 53/60

h) 32/72 - 21/18 = (-13/18)

Mình làm ngắn gọn nhanh nhất rồi đó, rút gon luôn rồi. nha