Tipping / not / custom / Viet Nam / so / you / not / have / tip / if / don't want .
=> Tipping is not a custom in Viet Nam, so you don't have to tip if you don't want to.
However / some / people / tip / because / they / think / service / good.
=> However , some people tip because they think the service is good .
In / countries / tipping / be / usual / thing . 
=> In some countries , tipping is a usual thing .
For example / in / US / people /  tip / 15 / 20 percent / of / bill / in / restaurant / cafe . 
=>  For example , in the US people tip 15 to 20 percent of the bill in the restaurant or cafe 

Ta có quy luật : 
6 : 2 = 3 
12 : 3 = 4 
20 : 4 = 5 
30 : 5 = 6 
42 : 6 = 7 
=> a : 9 = 8 
=> a = 9 . 8 
=> a = 72 

Gọi ƯCLN của 5a + 4 và 3a + 5 là m 
5a + 4 chia hết cho m <=> 15a + 12 chia hết cho m 
3a + 5 chia hết cho m <=> 15a + 20 chia hết cho m 
=> 15a + 12 - (15a + 20) chia hết cho m 
=> -8 chia hết cho m 
=> 5a + 4 và 3a + 5 không phải là 2 số nguyên tố cùng nhau 

Mỗi quả táo nặng : 30 : 3 = 10 
Hai nải chuối nặng : 18 - 10 = 8 
Mỗi nải chuối nặng : 8 : 2 = 4 
Quả dừa nặng : 4 - 2 = 2 
Tổng cân nặng một quả dừa , một quả táo và một nải chuối : 
2 + 10 + 4 = 16   
 

A = 3 + 3² +..... + 3¹⁰⁰ 
3A = 3² + 3³ + .... + 3¹⁰¹ 
3A - A = ( 3² + 3³ + .... + 3¹⁰¹ ) - ( 3 + 3² +..... + 3¹⁰⁰  )
2A = 3¹⁰¹ - 3
2A + 3 = 3ⁿ = 3¹⁰¹ 
=> n = 101
Chúc bạn học tốt !
 

100 km

1m²=0,0 001hm²

1m²=0,000 001km²

KHÔNG CHẮC LÀ ĐÚNG ĐÂU

31 học sinh , sao lớp này ít học sinh giỏi thế

1. A year has twelve months

 There are twelve months in a year.

2. He looks after the sick people

 He takes care of sick people

3. Do you enjoy listening to music?

 Are you interrested in listening to music?

4. What is your mother’s job?

 What does your mother do ?

5. We have a two- month summer vacation

 Our summer vacation lasts for two - month.

6. It takes me about two hours each day to do my homework

 I spend two hours each day to do my homework

7. Hoa is a hard student

 Hoa studies hard

8. It is not necessary for you to finish the work today

 You don’t have to finish the work today

9. Zidane is among the greatest football players in the world

 One of the greatest football player in the world is Zidane

10. Finding an apartment in a big city is not easy

It is not easy to find an apartment in a big city