Gọi số bạn lớp `9A` và `9B` lần lượt là `x` và `y`. Ta có:

`x+y=80`

`2x+3y=198`

`=> 160-2y+3y=198`

`=> y=38`

`=> x=42`

được CTVVIP tick câu trl

`=2(x+1)^2 +1 >=1 (`vì `2(x+1)^2 >=0, 1>0`)

`1`. is dancing

`2`. don't understand

`3`. doesn't wear

`4`. Do you like

`5`. is Leila reading

`=> 90xxy=4680`

`=>y=52`

Ta có: `2^3 +3^3=8+27=35`

` =>x=3`

`1`. did she go

`2`. did you do

`3`. works

`4`. ???

`5`. Have you wore

`6`. hasn't read

`7`. ???

`8`. Has she studied

`9`. Did we arrive

`10`. did you meet

The children always do their homework in the morning.

`c) C=126 ⋮ 3, 126⋮9`

`d) D=700` không chia hết cả `3` và `9`