4 If you aren't alert, you computer will be infected with viruses

5 If we use much pesticide on vegetables, they will become poisonous

9 Because Nam needs to improve his social skills, he attends the activity

11 How about using public buses instead of motorbike 

12 They enjoy protecting the environment unpolluted 

15 Mr Brown was disappointed that his son didn't write to him

1D 2B 3C 4A 5A 6C 7A 8A 9B 10A 11C 12D 13D 14D 15A 16D 17A 18C 19C 20D 21D 22C 23C 24A 25B 26C 27D 28B 29C

Chụp dọc đi bn oi!Chụp ngang thế này gãy cổ mất thôi!

11B và D

12A

13C

14D

15A

\(\frac{5}{11}.\frac{7}{25}+\frac{15}{11}.\frac{1}{5}\)

\(=\frac{5}{11}.\frac{7}{25}+\frac{5}{11}.3.\frac{1}{5}\)

\(=\frac{5}{11}.\frac{7}{25}+\frac{5}{11}.\frac{3}{5}\)

\(=\frac{5}{11}\left(\frac{7}{25}+\frac{3}{5}\right)\)

\(=\frac{5}{11}\left(\frac{7}{25}+\frac{15}{25}\right)\)

\(=\frac{5}{11}.\frac{22}{25}=\frac{2}{5}\)

2/5 nhé

   5/11x7/25+15/11x1/5

=5/11x(7/25+1/5)

=5/11x12/25

=12/55

Chúc bn hok tốt

a) chịu

b) ko biết

c)dốt

Mình ko viết đầu bài bn nhé 

a) (44 : 11 ) nhân ( 52 : 13 ) nhân ( 60 : 15 ) 

= 4 nhân 4 nhân 4 = 64 

b) = 123 nhân 456 nhân 1001 - 456 nhân 123 nhân 1001 

= 0

c) 14 nhân ( 29 + 71 ) + ( 1 + 2 + 3 + ... + 99 ) nhân ( 199 nhân 1001 nhân 198 - 1998 nhân 1001 nhân 199 )

= 14 nhân 100 + 0 = 1400 

chúc bn học tốt

Cảm ơn ông rất nhiều

\(=-18\)

\(6-7-8+9-10+11+12-13+14-15-16+17-18\)

\(=\left(6-7-8+9\right)+\left(-10+11+12-13\right)+\left(14-15-16+17\right)-18\)

\(=0+0+0-18\)

\(=0-18\)

\(=-18\)