Bài 3: 

Ta có: a//b

nên \(x+y=180\)

mà \(2x-3y=0\)

nên \(\left\{{}\begin{matrix}x+y=180\\2x-3y=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x+2y=180\\2x-3y=0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}5y=180\\x+y=180\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=36\\x=144\end{matrix}\right.\)

C

1 cooking 

2 listening

3 reading

4 playing

5 cycling

1 People collect a lot of things such as stamps, milk bottle labels, comic books as well as car toys

2 She is 20 years old

3 She is a hairdresser

4 It is collecting candy shells

5 Her friends and relatives

B

1 F

2 F

3 F

4 F

5 T

where do you think people will live ?

Where do you think people will live?

where do you think people will live?

`a)1001^2`

`=(1000+1)^2=1000000+2000+1`

`=1002001`

`b)29,9.30,1`

`=(30-0,1)(30+0,1)`

`=30^2-0,1^2`

`=900-0,01=899,99`

`c)199^2=(200-1)^2`

`=40000-400+1`

`=39601`

`d)84^2-16^2`

`=(84-16)(84+16)`

`=100.68`

`=6800`

`e)313^2-312^2`

`=(313-312)(313+312)`

`=625`

`f)47.53`

`=(50-3)(50+3)`

`=2500-9=2491`

x-(5-x)=x-15

<=>x-5+x=x-15

<=>x-5+x-x+15=0

<=>x+10=0

<=>x=-10

Vậy x=-10

Bài làm

x - ( 5 - x ) = x - 15

=> x - 5 + x - x + 15 = 0

=> 10 - x = 0

=> x = 10

Vậy x = 10

Mik lm sai nha, phải ra là 10+x mới đúng nha. Vì x - 5 + x - x + 15 = 0

Thì phải gộp ( x + x - x ) + ( -5 + 15 ) = 0

=>X + 10 = 0

=> X = -10