20,10x35-19,45x65+20,10x65-19,45x35

=(35+65)x20,10+(35+65)x19,45

=100x20,10-100x19,45

=100x(20,10-19,45)

=100x0,65=65

b: =19,45x10=194,5

mn ơi mn giúp mik với 

= 35*(20,10-19,45)+65*(20,10-19,45)

=35*0,65+65*0,65

=0,65*(35+65)

=0,65*100

=65

19,45*30,4+69,6*19,45 =19,5*(30,4+69,6)=19,5*100=1950

a)19,45 x 30,4 + 69,6 x 19,45

= 19,45 x ( 30,4 + 69,6 )

= 19,45 x 100

= 1945

b)148,6 x 0,09 - 0,08 x 148,6

= 148,6 x ( 0,09 - 0,08 )

= 148,6 x 0,01

= 1,486

c)82,05 : 1,25 - 69,55 : 1,25

= 1,25 : ( 82,05 - 69,55 )

= 1,25 : 12,5

= 0,1

d) ( 123,6 x 3,85 ) : 41,2

= ( 123,6 : 41,2 ) x 3,85

= 3 : 3,85

= 0,78

a.54,01    

a.54,01

\(12,3x=142,45-19,45\)

\(12,3x=123\)

\(x=10\)

vậy \(x=10\)

\(\left(3x-0,8\right):x+14,5=15\)

\(\left(3x-0,8\right):x=0,5\)

\(3-\frac{0,8}{x}=0,5\)

\(\frac{0,8}{x}=2,5\)

\(\Rightarrow x=0,32\)

vậy \(x=0,32\)

\(4,85+12,5x=5,58\)

\(12,5x=5,58-4,85\)

\(12,5x=0,73\)

\(x=0,0584\)

x * 12,3 = 142,45 - 19,45

=> x * 12,3 = 123

=> x = 123 : 12,3

=> x= 10

4,85 + x * 12,5 = 5,58

=> x * 12,5 = 5,58 - 4,85

=> x * 12,5 = 0,73

=> x = 0,73 : 12,5

=> x = 0,0584 

a: \(\Leftrightarrow x\cdot12.3=123\)

=>x=10

b: \(\dfrac{3x-0.8}{x}+14.5=15\)

\(\Leftrightarrow\dfrac{3x-0.8}{x}=0.5\)

\(\Leftrightarrow3x-0.8=0.5x\)

=>2,5x=0,8

hay x=8/25

c: \(\Leftrightarrow12.5\cdot x=5.58-4.85=0.73\)

hay x=73/1250