Kẻ đường thẳng t qua O song song với Ac

=> \(\widehat{tOA}=\widehat{CAO}=30^o\) (so le trong)

Ta có: a // b (gt)

\(\Rightarrow\widehat{tOB}=\widehat{OBD}=60^o\) (so le trong)

=> \(\widehat{x}=\widehat{AOt}+\widehat{BOt}=60^o+30^o=90^o\)

are (ko nhìn rõ đề)

cycling

started

is

to work

to donate

are controlled 

is

renamed 
does not like 
was reconstructed 
do not usually go 
is made 
have ever tried 
has increased 
will you take
was used 
taking

51. to speak -> speaking

52. informations -> information (information là uncountable noun)

53. my -> mine

54. many -> much (time là uncountable noun)

55. three -> third

56. to

57. up (look up: tra từ điển)

58. after (name after: đc đặt tên theo..)

59. on (put on weight: tăng cân)

60. down (sound down: buồn)

very good! ⚡

nón lá, đầu bút chì, kem ốc quế,...

+Kim tự tháp 

+đầu tên lửa

+ nón lá

Nón lá, mũ sinh nhật, cọc tiêu nhựa

\(x\times3-1256=2344\)
\(x\times3=2344+1256\)
\(x\times3=3600\)
\(x=3600:3\)
\(x=1200\)

1200

\(x\times3=2344+1256\)

\(x\times3=3600\)

\(x=3600:3\)

\(x=1200\)

\(a,=-17+91-91+17+2011=\left(-17+17\right)+\left(91-91\right)+2011\)

\(=0+0+2011=2011\)

b)\(=\dfrac{4}{7}+\dfrac{1}{6}-0,375.4=\dfrac{31}{42}-\dfrac{3}{2}=-\dfrac{16}{21}\)

\(b)\) \(\dfrac{4}{7}\) + \(\dfrac{5}{6}\) : \(5\) \(- 0,375 .(-2)\)²\(=\) \(\dfrac{4}{7}\) + \(\dfrac{1}{6}\) - \(0,375\) . \(4\)

= \(\dfrac{4}{7}\) + \(\dfrac{1}{6}\) - \(\dfrac{3}{2}\) = \(\dfrac{4.6}{42}\) +  \(\dfrac{1.7}{42}\) - \(\dfrac{3.21}{42}\) = \(-\)\(\dfrac{16}{21}\)