I agree with the opinion that people should read more books and watch less TV. Nowaday, TV is becoming more and more popular in people's lives. Because of that, books are forgotten and maybe are thrown away. That's a shame because books contain many interesting and amazing things. I don't mean that TV is less interesting than books, I mean books are very important to us. Actually, books help us relax and widen our knowledge too. TVs are making our eyes tired and sore, but books aren't. So please read more books and do it as your daily life activity. Books are our friends so don't throw them away like how other people do.

Chúc bạn học tốt!!!

-x-2/3=-6/7

=> -x= -6/7 +2/3

=> -x =-4/21

=>x=4/21

Vì xOy là góc bẹt => xOa và yOa là 2 góc kề bù

Vì xOa và yOa là 2 góc kề bù

=> xOa + yOa = 180^o       (1)

Thay xOa = 100^o vào (1) ta có :

100^o + yOa = 180^o

              yOa = 180^o - 100^o

              yOa = 80^o

Vì Ob là tia phân giác của yOa

=> \(yOb=bOa=\frac{yOa}{2}=\frac{80^o}{2}=40^o\)

Vì xOb và yOb là 2 góc kề bù

=> xOb + yOb = 180^o     (2)

Thay yOb = 40^o vào (2) ta có : 

xOb + 40^o = 180^o

xOb = 180^o - 40^o

xOb = 140^o

Dấu góc bạn tự ghi nha

k mk nhé believe in yourself, mk âm nhiều lắm !