tính nhanh =400

tìm x=15

k chomki,mik k lại

tính nhanh :

10 + 20 + 50 + 90 + 100 + 80 + 50

= (10 + 90) + (20 + 80) + (50 + 50) + 100

=      100    +       100    +     100    +  100

=      100 x 4 

=    400

tìm x :

x + 5 = 10 x 2

x + 5 = 20

       x = 20 - 5

       x = 15

tchs mình tch lại

10+20+50+90+100+80+50

=(10+90)+(20+80)+(50+50)+100

=100+100+100+100

=100x4

=400

x+5=10x2

=>x+5=20

=>x=20:5

=>x=4

=(250-50)- (0,95x40)x(10x0,1)x(0,125x80)
=200 - (38 x1x10)
=200-380
=-180 
 

99570

99,570

= ( 60 + 50+40+30+20+10 ) x 2000 + 1500

= 210 x 2000 + 1500

=  420000 + 1500

= 421500

= 421500 nha bn, nhớ k mk nha

=421500

20 + 60 + 50 + 80 + 90 + 10 + 50 + 60 x 10

= (20 + 80) + (50 + 50 ) + (90 + 10 ) + 600 + 60

=     100     +      100     +      100     + 660

=              960

=(20+80)+(50+50)+(90+10)+(60*10)+60

=100+100+100+600+60

=960

20 + 60 + 50 + 80 + 90 + 10 + 50 + 60 x 10

= 20 + 60 + 50 + 80 + 90 + 10 + 50 + 600

= ( 20 + 80 ) + ( 50 + 50 ) + ( 90 + 10 ) + 60 + 600

= 100 + 100 + 100 + 60 + 600

= 100 . 3 + 660

= 300 + 660

= 960

=5110

k mk đi mk k bn rùi 

đó n,nha !!!!!!!!!!!

50 + 50 + 50 + 50 x 10 x 10 + 10

= (50 + 50) + 50 x 10 x 10 + 10

=     100     + 500 x 10 + 10

=     100     +     5000   + 10

     = 5110

=5110

a)X=100

b)X=70

K MKNHA BN

x + 20 - 10 = 110

x + 20 = 110 + 10

x + 20 = 120

x = 120 - 20

x = 100

x + 80 - 50 = 100

x + 80 = 100 + 50

x + 80 = 150

x = 150 - 80

x = 70

x+ 20= 110+10

x+20= 120

      x= 120-20

      x= 100

x+80= 100+50

x+80= 150

      x= 150-80

      x=70 

k nhé

\(\frac{x+10}{90}+\frac{x+20}{80}+\frac{x+30}{70}+\frac{x+40}{60}+\frac{x+50}{50}=-5\)

<=> \(\frac{x+10}{90}+1+\frac{x+20}{80}+1+\frac{x+30}{70}+1+\frac{x+40}{60}+1+\frac{x+50}{50}+1=0\)

<=> \(\frac{x+100}{90}+\frac{x+100}{80}+\frac{x+100}{70}+\frac{x+100}{60}+\frac{x+100}{50}=0\)

<=> \(\left(x+100\right)\left(\frac{1}{90}+\frac{1}{80}+\frac{1}{70}+\frac{1}{60}+\frac{1}{50}\right)=0\)

<=> x + 100 = 0 

<=> x = -100

Vậy x = -100

50 x 2 + 8 x 50

= (2 + 8) x 50

=     10   x 50

=       500

10 + 10 + 10 + 50 + 50 + 10 + 10

= (10 x 5) + (50 + 50)

=     50     +     100

=         150

50 x 2 + 8 x 50 

= 50 x ( 2 + 8 ) 

= 50 x    10 

= 500

10 + 10 + 10 + 50 + 50 + 10 + 10

= 10 x 5 + 50 x 5 

=    50    +   250

=         300

50x2+8x50

=50x(8+2)

=50x10

500

10+10+10+50+50+10

=10x5+50+50

=50+50+50

=50x3

=150