1 ) ( x - 15 ) : 2 = 10

x - 15 = 10 x 2

x - 15 = 20

x = 20 + 15

x = 35

2 ) 19 - 9 . ( x - 10 ) = 1

9 . ( x - 10 ) = 19 - 1

9 . ( x - 10 ) = 18

x - 10 = 18 : 9

x - 10 = 2

x = 10 + 2 

x = 12

21 . x + 21 . 10 = 2100

21 . ( x + 10 ) = 2100

x + 10 = 2100 : 21

x + 10 = 100

x = 100 - 10

x = 90

( x - 15 ) :2 = 10

 x - 15     = 10 : 2

x - 15        = 5

x               = 5 + 15

x                20

19 - 9 * ( x - 10 ) = 1

       9 * ( x - 10 ) = 19 -1

       9 *  ( x - 10 ) = 18

                x - 10= 18:9

                 x - 10 = 2

                 x         = 2 +10

                x          = 12

21 * x + 21 * 10 = 2100

21 * ( x + 10 )     = 2100

          x + 10      = 2100 : 21

          x + 10      =100

           x             = 100 - 10

            x             = 90

= 10×10

= 100

K mk nhé

*Mio*

10x10=100

10+10+10+10+10+10+10+10+10+10=10x10=100

 \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\) \(\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)

\(=\dfrac{1+2+3+4+5+6+7+8+9}{10}\)

\(=\dfrac{45}{10}=\dfrac{9}{2}\)

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9/10 = 44/10 = 22/5

bằng 9/2 nhé

\(B=\frac{-9}{10}.\frac{5}{14}+\frac{1}{10}.\frac{-9}{2}+\frac{1}{7}.\frac{-9}{10}\)
\(B=\frac{-9}{2}.\frac{1}{14}+\frac{-9}{20}+\frac{-9}{70}\)
\(B=\frac{-9}{28}+\frac{-9}{20}+\frac{-9}{70}\)
\(B=\frac{-27}{35}+\frac{-9}{70}\)
\(B=-\frac{9}{10}\)

( 1400 + 60 ) : 10

= 1400 : 10 + 60 : 10

= 140 + 6

= 146

( 2100 - 42 ) : 21

= 2100 : 21 - 42 : 21

= 100 - 2

= 98

(1400+60)/10

=1400/10+60/10

=140+6

=146

b, ( 2100 - 42 ) /21

=2100 / 21 + 42 / 21

=100+2

=102

(1400+60):10

=1460:10

=146

(2100-42):21

=2100:21-42:21

=100-2

=98

63.10+63.20+63.30+63.40

= 63 . ( 10 + 20 + 30 + 40 ) 

= 63 . 100

= 6300

 50 + 10 + 50 + 10

= 100 + 20

= 120 

\(63.10+63.20+63.30+63.40\)

\(=63.\left(10+20+30+40\right)\)

\(=63.100\)

\(=6300\)

\(50+10+50+10\)

\(\left(50+50\right)+\left(10+10\right)\)

\(=100+20\)

\(=120\)

63 x 10 + 63 x 20 + 63 x 30 + 63 x 40 

= 63 x ( 10 + 20 + 30 + 40 )

= 63 x 100

= 6300

50 + 10 + 50 + 10 

= ( 50 + 50 ) + ( 10 + 10 ) 

= 100 + 20 

= 120

x+500+10=2100

x+(500+10)=2100

x+510=2100

x=2100-510

x=1590

x=1590

chẩn 100%nha !

tk mk nha !

x + 500 + 10 = 2100

<=> x + 510 = 2100

<=> x = 2100 - 510

=> x = 1590

ai tk mk mk tk lại nha