x = 51/35 - 25/48 = 1573/1680

Ta có x bằng:

51/35 - 25/48.Mà mẫu chung của 35 và 48 là 1680.

51/35=51×48/35×48=2448/1680

25/48=25×35/48×35=875/1680

Vậy 51/35-25/48=2448/1680-875/1680=1573/1680

a)  

\(\dfrac{1}{2}=0,5;\dfrac{3}{4}=0,75;\dfrac{7}{5}=1,4;\dfrac{9}{8}=1,125;\dfrac{26}{25}=1,04;\dfrac{120}{125}=0,96\)

b) 

\(\dfrac{15}{25}=0,6;\dfrac{75}{25}=3;\dfrac{90}{300}=0,3;\dfrac{27}{36}=0,75;\dfrac{51}{85}=0,6\)

a,1/2=5/10;3/4=75/100;7/5=140/100;26/25=108/100;120/125=960/1000

b,15/25=60/100;75/25=300/100;90/300=3/10;27/36=3/4=75/100;

51/85=3/5=60/100;39/65=3/5=60/100

(25+51)+(42-25-53-51)=25+51+42-25-53-51=42-53=-11

\(\left(25+51\right)+\left(45-25-53-51\right)\)

\(=25+51+45-25-53-51\)

\(=\left(25-25\right)+\left(51-51\right)+45-53\)

\(=0+0+45-53\)

\(=-8\)

\(\left(25+51\right)+\left(45-25-53-51\right)\)

\(=25+51+45-25-53-51\)

\(=\left(25-25\right)+\left(51-51\right)+45-53\)

\(=0+0+45-53\)

\(=45-53\)

\(=-8\)

= 25 + 51 + 42 - 25 - 53 - 51 

= (25-25) +( 51 -51) +42-53

= 0+0+42-53 =-11 

ai tick mình cho tròn 205 với

(25+51)+(42-25-53-51)

  ( 25 + 51 ) + ( 42 - 25 - 53 - 51 )

= 25 + 51 + 42 - 25 - 53 - 51

= (25 - 25) + (51- 51) + (42 - 53)

= -11

(15+21)+(25-15-35-21)

=15+21+25-15-35-21

=[15-15]+[21-21]+[35-15]

=0+0+20

=20

(25+51)+(42-25-53-51)

= 25+51+42-25-53-51

=[25-25]+[51-51]+[42-53]

=0+0+(-11)

=-11