10 + 20 = 50 - x 

30 = 50 - x 

x = 50 - 30

x = 20 

10 + 20 = 50 - x

30 = 50 - x

x = 20

10 + 90 = 10 + x

100 = 10 + x

x = 90

\(10+20=50-x\)

\(30=50-x\)

   \(x=50-30\)

   \(x=20\)

\(10+90=10+x\)

\(100=10+x\)

     \(x=100-10\)

     \(x=90\)

x=5

x=0 nha bn

chuẩn ko cần chỉnh nếu các bạn nghĩ giống mik thì ủng hộ mik nha

x=5&x=10

bài làm:

5+10=20-x

    15=20-x

      x=20-15

      x=5

10+40=50-x

      50=50-x

        x=50-50

        x=0

TÍCH MIK NHA BẠN

a)x+10=30

=>x=20

b)x+10-5=20+20

x+10-5=40

x+10=45

=>x=35

x + 10 = 50 - 20

x + 10 = 30

x = 20 

x + 10 - 5 = 20 + 20

x + 5 = 40

x = 35 

\(x+10=50-20\)

\(x+10=30\)

\(x=30-10\)

\(x=20\)

\(x+10-5=20+20\)

\(x+5=40\)

\(x=40-5\)

\(x=35\)

10+x=20:5+50

10+x=4+50

10+x=54

x=54-10

X=44

10 +x=54

x=54-10

x=44

10+x=20:5+50

10+x= 4+50

10+x=45

x=45-10

x=35

Vậy x= 35

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

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