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 

a) x.4/5:2=6/7                                                              

    x.4/5=6/7*2

    x.4/5=12/7

    x=12/7:4/5

    x=15/7

b) 6/5:x:5/4=10/15

    6/5:x=10/15*5/4

    6/5:x=5/6

    x=6/5:5/6

    x=36/25

15 x 5 + 3 x 5 + 5 x 2 - 10 x 5

= 5 x(15 + 3 + 2 - 10)

= 5 x 10

= 50

=5x(15+3+5+2-10)

=5x10

=50

5+6+7+8+9

=35

5+6+7+8+9+10

=45

10+9-8+7-6+5-4+3-2+1-0

= 10 +[(9 - 8) + (7 - 6) + (5 - 4) + (3 - 2) + (1 - 0)]

= 10 + [1 + 1 + 1 + 1 + 1]

= 10 + 1 x 5

= 10 + 5

= 15

15

0 nha :3

1 + 1 - 2 + 14 - 4 + 20 - 15 + 10 - 5 + 100 - 60 x 2

= (1 + 1 - 2) + (14 - 4) + (20 - 10) + (15 - 5) + 100 - 120

= (2 - 2) + 10 + 10 + 10 + 100 - 120

= 130 - 120

= 10

\(\frac{10}{5}\)\(=10:5=2\)

nhớ k mk nha

= 2

tk mk nha bn

Số số hạng của dãy số là:

10-0+1=11(số)

Tổng của dãy số là: \(\left(10+0\right)\times\frac{11}{2}=10\times\frac{11}{2}=5\times11=55\)

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1+2+3+4+5+6+7+8+9+10+11=66

1+2+3+4+5+6+7+8+9+10+11=66

1+5+4+10=20

k cho mình đi

20 nha bạn 

hok tốt ^_^