683 x 35 = 23905

1654 x 425 = 702950

2438 x 306 = 746028

7/9 x 3/35 = 1/15 ( rút gọn )

15,7 ; 6,28 = 2,5

11/17 : 33/34 = 2/3 ( rút gọn )

36,66 : 7,8 = 4,7 

15,7 : 6,28 = 2,5 ( lặp câu nè bạn )

27,63 : 0,45 = 61,4

683 x 35 = 23905

1654 x 425 = 702950

2438 x 306 = 746028

\(\frac{7}{9}\)x \(\frac{3}{35}\)= \(\frac{1}{15}\)

15,7 : 6,28 = 2,5

\(\frac{11}{17}\): \(\frac{33}{34}\)= \(\frac{2}{3}\)

36,66 : 7,8 = 4,7

15,7 : 6,28 = 2,5

27,63 : 0,45 = 61,4

1) =23905

2 =702950

3) =746028

4) =1/5

5) =5/2

6) =2/3

7) =47/10

8) =5/2

9) =307/5=61,4

6) =2/2

37.15 + 37.45 + 74.20

= 37.15 + 37.45 + 37.2.20

= 37.15 + 37.45 + 37.40

= 37( 15 + 45 + 40 )

= 37.100 = 3700

3 + 7 + 11 + 15 + 19 + 23 + 27 + 31 + 35

= ( 3 + 27 ) + ( 7 + 23 ) + ( 11 + 19 ) + ( 15 + 35 ) + 31

= 30 + 30 + 30 + 50 + 31 = 171

x + ( x + 1 ) + ( x + 2 ) + ( x + 3 ) + ... + ( x + 10 ) = 2029099

( x + x + x +... + x ) + ( 1 + 2 + 3 + ... + 10 ) = 2029099

11x +  55 = 2029099

ez rồi tự tính 

BT1 :thực hành phép tính

4/3+-11/31+3/10-20/31-2/5 = 7/30

7/12-1/-16+3/4 = 67/48

2/11.-5/4+-9/11.5/4+ 1 và 3/4 = -1/4 * và 3/4 là sao bạn *

-9/27-25/75 = -2/3

a)\(\frac{27}{5}\text{x}\frac{91}{12}\text{x}\frac{125}{9}\text{x}\frac{96}{13}=\frac{27}{9}\text{x}\frac{91}{13}\text{x}\frac{125}{5}\text{x}\frac{96}{12}=3\text{x}7\text{x}25\text{x}8\)

Đến đây tự tính nha !

b)\(\frac{2539}{35}\text{x}\frac{7}{90}+\frac{561}{35}\text{x}\frac{7}{90}=\frac{7}{90}\text{x}\left(\frac{2539}{35}+\frac{561}{35}\right)=\frac{7}{90}\text{x}\frac{3100}{35}=\frac{3100}{90}\text{x}\frac{7}{35}=\frac{310}{9}\text{x}\frac{1}{5}=\frac{62}{9}\)

1. 27/5 x 91/12 x 125/9 x 96/13

2. 2539/35 x 7/90 + 561/35 x 7/90

3. 31/7 : (2/5 x 31/7)

4. (29 x 15/23 x 36/29) : 5/23

3)\(\dfrac{31}{7}\) : (\(\dfrac{2}{5}\times\dfrac{31}{7}\) )

=\(\dfrac{31}{7}\) : \(\dfrac{2}{5}\times\dfrac{31}{7}\)

= \(\dfrac{31}{7}:\dfrac{31}{7}\times\dfrac{2}{5}\)

= \(\dfrac{2}{5}\)

4) (\(29\times\dfrac{15}{23}\times\dfrac{31}{7}\)) : \(\dfrac{5}{23}\) 

=\(29\times\dfrac{15}{23}\times\dfrac{31}{7}:\dfrac{5}{23}\)

= \(29\times\dfrac{31}{7}\times\dfrac{15}{23}:\dfrac{5}{23}\)

= 29 x \(\dfrac{31}{7}\times\dfrac{15}{23}\times\dfrac{23}{5}\)

= 29 x \(\dfrac{31}{7}\times3\)

= 29 x 3 x \(\dfrac{31}{7}\) 

= 87 x \(\dfrac{31}{7}\) 

= \(\dfrac{2697}{7}\)

Bài 2:

a: 5/7-3/7x=1

=>3/7x=-2/7

hay x=-2/3

b: \(x+\dfrac{2}{3}=\dfrac{-1}{12}\cdot\dfrac{-4}{5}=\dfrac{1}{15}\)

=>x=1/15-2/3=-9/15=-3/5

c: \(x-4=\dfrac{-14}{35}:\dfrac{7}{5}=\dfrac{-14}{35}\cdot\dfrac{5}{7}=\dfrac{-70}{245}=\dfrac{-2}{7}\)

=>x=4-2/7=26/7

A)  7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11

=7/38.(9/11+4/11-2/11)

=7/38

B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20

=5/31.(21/25-7/10-9/20)

=5/31.(-31/100)

=-1/20