1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 

= ( 1 + 19 ) + ( 3 + 17 ) + ( 5 + 15 ) + ( 7 + 13 ) + ( 9 + 11 )

=    20        +   20        +      20       +     20       + 20 

= 20 x 5 

= 100

what nghĩa là cái gì

thì là mày quá ngu nên khộng hiểu đâu

Chắc là 60 năm nữa

bai 2 :dat cac chang tu chi tang suat vao vi tri dung o cau

3.we have fish for din ne r .(seldom)

4.peter dones't get up before seven . (usually)

5. they watch TV in the afternoom.(never)

6.how do you go sphopping? (often)

7.I don't do my homework after shool (hardly)

8. the shool bus arrives at seven . (every day)

1. He plays golf on sundays.(sometimes)

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2.the weather í dab in november.(always)