-5 + (-37 - 45 + 51) - (-37 + 51)

=  -5  - 37 - 45 + 51 + 37 - 51

=  - (5 + 45) - (37 - 37) + (51 - 51)

= - 50 - 0 + 0

= - 50

  - (15 - 47 + 58) + (15 - 47 ) + 3

= - 15 + 47 - 58 + 15 - 47 + 3

= (-15 + 15) + (47 - 47) - (58 - 3)

= 0 + 0 - 55

= - 55

  (53 - 45 - 49) - (53 + 45 - 49)

= 53 -  45 - 49 - 53 - 45 + 49

= (53 - 53) + (-49 + 49) - (45 + 45)

= 0 + 0 - 90

= - 90 

    13 - 15 + 49 - 13 + 15 - 48

=  (13 - 13) + (-15 + 15) + (49 - 48)

= 0 + 0 + 1

=  1 

15+13 -15-13 +49-48

mình sẽ  giải cho bạn nhưng mình ko phải là  khoa  mà là quan anh bạn của khoa

45 x 16 - 17 / 45 x 15 + 28 = 45 x ( 15 + 1 ) - 17 = 45 x 15 + 45 - 17 / 45 x 15 + 28= 45 x 15 + 28 / 45 x 15 + 28=1

45.16-17/45.15+28

=45.15+(45-17)/45.15+28

=45.15+28/45.15+28

=1

\(\frac{45\cdot16-17}{45\cdot15+28}\)

\(=\frac{45\cdot15+45-17}{45\cdot15+28}\)

\(=\frac{45\cdot15+28}{45\cdot15+28}\)

\(=1\)

\(\frac{45\times116-17}{45\times115+28}=\frac{45\times115-17+45}{45\times115+28}=\frac{45\times115+28}{45\times115+28}=1\)

45⋅16−17​

=\frac{45\cdot15+45-17}{45\cdot15+28}=45⋅15+2845⋅15+45−17​

=\frac{45\cdot15+28}{45\cdot15+28}=45⋅15+2845⋅15+28

$=1$

a,
       85.(35-27)-35.(85-27)
     =85.35-85.27-35.85-35.27
     =85.35-35.85-85.27.35.27
     =85.27-35.27
     =(85-35).27
     =100.27/2
     =2700/2
     =1350

45-58+(-45)+(+58)-3=45-58-45+58-3=(45-45)+(58-58)-3=-3

(-57)-(-12)+3-(-57)=-57+12+3+57=(-57+57)+12+3=15

-(-24)-(-30)+(-24)-30+8=24+30-24-30+8=(24-24)+(30-30)+8=8

-(-12)+(+19)-(+12)+8-19=12+19-12+8-19=(12-12)+(19-19)+8=8

47-(-53)+(-47)-(+53)=47+53-47-53=(47-47)+(53-53)=0

-(+28)+32-(-28)+(-34)=-28+32+28-34=(-28+28)-(34-32)=-2

15-(+72)+(-15)+(+72)=15-72-15+72=(15-15)+(72-72)=0

20-(+46)+(-25)-(-46)=20-46-25+46=(20-25)+(46-46)=-5

28-(-32)+(-28)-32+5=28+32-28-32+5=(28-28)+(32-32)+5=5

-75+(-49)+(+75)+49-12=-75-49+75+49-12=(-75+75)+(49-49)-12=-12

\(...=45-58-45+58-3=-3\)

\(...=-57+12+3+57=15\)

\(...=24+30-24-30+8=8\)

\(...=12+19-12+8-19=8\)

\(...=47+53-47-53=0\)

\(...=-28+32+28-34=-2\)

\(...=15-72-15+72=0\)

\(...=20-46-25+46=-5\)

\(=...28+32-28-32+5=5\)

\(...=-75-49+75+49-12=-12\)

a, 21.35-3.25.7=21.35-21.25=21.(35-25)=21.10=210

b, 77-11.(30+7)=77-330-77=-330

c, 85.(35-27)-35.(85-27)=85.35-85.27-35.85+35.27=0

d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-2(47.15)=1410

a, 21.35-3.25.7=21.35-21.25=21.10=210

b,77-11.(30+7)=77-11.30-11.7=-11.30=-330

c,85.(35-27)-35.(85-27)=85.35-85.27-85.35+35.27=27.(-50)=-1350

d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-47.30=-1410

a, 21 . 35 - 3 . 25 . 7

= (21 . 35) - (3 . 25 . 7)

= 735 - 525

= 210

b, 77-11.(30+7)

= 77 - 11.30 - 11.7

= -11.30

= -330

c, 85.(35-27)-35.(85-27)

= 85.35 - 85.27 - 85.35 + 35.27

= 27.(-50)

= -1350

d, 47.(45-15)-47.(45+15)

= 47.45 - 47.15 - 47.45 - 47.15

= -47.30

= -1410

12+45+54+47+87=245 hok tốt

12 + 45 + 54 + 47 + 87

= 57 + 54 + 47 + 87

= 111 + 47 + 87

= 158 + 87

= 245

12 + 45 + 54+ 47 + 87

= 57 + 101 + 87

=158 + 87

=245

21.35-3.25.7

= 21.35-21.25

= 21.(35-25)

= 21. 10

=210

77 - 11.( 30+7)

= 11.7 -11.30 -11.7

= 11.7-11.7 -11.30

= -11.30

= -330

21.35-3.25.7=210

77-11(30+7)=-330

85(35-27)-35(85-27)=-1350

47(45-15)-47(45+15)=-2820

a)21.35-3.25.7

=21.35-(3.7).25

=21.35-21.25

=21.(35-25)

=21.10=210