a) 48 : 6 : 2 = 4

48 : 6 x 2 = 16

b) 27 : 9 x 3 = 9

27 : 9 : 3 = 1

a) 5 x 7 + 14

= 35 + 14

= 49

b) 48 : 6 + 13

= 8 +13

= 21

c) 6 x 8 – 26

= 48 – 26

= 22

d) 24 - 4 x 5

= 24 – 20

= 4

2. Tính (+5) + ( +4) = 9

3.Tính (- 9) + ( - 1) = -10

4.Tính : 28 + (-15) = 13

5.Tính (-15) + 12 = - 3

6.Tính (-25) + 25 = 0

7.Tính : 13 - 17 = - 4

8.Tính : (-78) - 9 = - 87

9.Tính : ( -24) - ( - 16) = - 8

10.Tính : 17 - (-3) = 20

11.Tính nhanh : (-21) - ( 48 + 52 - 21) = -100

2,  (+5)+(+4)=+9 hoạc 9 cũng được

3,  (-9)+(-1)=-10

4,  28+(-15)=13

5,  (-15)+12=-3

6,  (-25)+25=0

7,  13-17=4

8,   (-78)-9=-87

9,  (-24)-(-16)=-40

10, 17-(-3)=20

11,  (-21+21)-(48-52)=-4

2.  (+5) + ( +4) = 9

3. (- 9) + ( - 1) = -10

4. 28 + (-15) = 13

5. (-15) + 12 = - 3

6. (-25) + 25 = 0

7. 13 - 17 = - 4

8. (-78) - 9 = - 87

9.( -24) - ( - 16) = - 8

10. 17 - (-3) = 20

11. (-21) - ( 48 + 52 - 21) = -100

a) y - 6 chia 2 - ( 48 - 24 x 2 chia 6 - 3 ) = 0

=> y - 6 chia 2 - ( 48 - 48 chia 6 - 3 ) = 0 

=> y - 6 chia 2 - (  48 - 8 -3 ) = 0

= > y - 6 chia 2 - 37 = 0

=> y - 6 chia 2 = 0 + 37 

=> y - 6 chia 2 = 37

=> y -6 = 37 chia 2 

=> y - 6 = 37 / 2

=> y = 37 / 2    +  6

=> y = 49 / 2

Vậy y = 49 / 2

b) ( 7 x 13 + 8 x 13 ) chia ( 92 /3-y ) = 39

=> ( 91  +   104 ) chia ( 92/3 - y ) =39

=> 195 chia  ( 92 /3 - y ) = 39

=> 92/3 - y = 7605 

=>           y = 7605 + 92/3 

=>           y = 22907 /3

Vậy y = 22907 / 3

\(\dfrac{7}{18}=\dfrac{7.4}{18.4}=\dfrac{28}{72}\); \(\dfrac{9}{8}=\dfrac{9.9}{8.9}=\dfrac{81}{72}\)

\(\dfrac{2}{3}=\dfrac{2.20}{3.20}=\dfrac{40}{60};\dfrac{3}{4}=\dfrac{3.15}{4.15}=\dfrac{45}{60};\dfrac{6}{5}=\dfrac{6.12}{5.12}=\dfrac{72}{60}\)

\(\dfrac{13}{12}=\dfrac{13.5}{12.5}=\dfrac{65}{60};\dfrac{5}{6}=\dfrac{5.10}{6.10}=\dfrac{50}{60};\dfrac{4}{5}=\dfrac{4.12}{12.5}=\dfrac{48}{60}\)

\(\dfrac{9}{8}=\dfrac{9.8}{8.6}=\dfrac{72}{48};\dfrac{7}{24}=\dfrac{7.2}{24.2}=\dfrac{14}{48};\dfrac{41}{48}\)

1)  \(35.18-5.7.28=35.18-35.28=35\left(18-28\right)=-350\)

2)  \(45-5\left(12+9\right)=45-60-45=-60\)

3)  \(24\left(16-5\right)-16\left(24-5\right)=24.16-24.5-16.24+16.5=5\left(16-24\right)=5.8=40\)

4)  \(29\left(19-13\right)-19\left(29-13\right)=29.19-29.13-19.29+19.13=13\left(19-29\right)=-130\)

5)  \(31.\left(-18\right)+31.\left(-81\right)-31=-31.\left(18+81+1\right)=-3100\)

6)  \(\left(-12\right).47+\left(-12\right).52+\left(-12\right)=\left(-12\right)\left(47+52+1\right)=-1200\)

7)  \(13\left(23+22\right)-3\left(17+28\right)=13.45-3.45=45.\left(13-3\right)=450\)

8)  \(-48+48.\left(-78\right)+48.\left(-21\right)=-48\left(1+78+21\right)=-4800\)

1, 35 . 18 - 5 . 7 . 28

= 35 . 18 - 35 . 28

= 35 . ( 18 - 28 )

= 35 . ( -10 )

= -350

2, 45 - 5 . ( 12 + 9 )

= 40 . 21

= 840

3, 24 . ( 16 - 5 ) - 16 . ( 24 - 5 )

= 24 . 11 - 16 . 19

= 264 - 304

= -40