Cô nói rằng nghiên cứu không cho thấy sự cần thiết phải nghiên cứu hay không có hậu quả lâu dài của tiếp xúc lặp đi lặp lại trong nhiều năm.

1) Yesterday, I went to the restaurant with my my parents.

2) We drove around the parking lot for 20 mins to find a parking space last week.

3) I didn't go to school last Sunday.

People aged 65 and over now contain nearly 20% of the population.

Paris is one of the most expensive cities in the world.

sao lại có 2 house nhỉ

C. best

Hình đại khái là như thế

a)\(\frac{x}{15}=\frac{2}{5}\Rightarrow x=\frac{2\cdot15}{5}=6\)

b)\(\frac{3}{x\cdot7}=\frac{27}{135}\Rightarrow x\cdot7=\frac{3\cdot135}{27}\Rightarrow x\cdot7=15\Rightarrow x=2\frac{1}{7}\)

a)\(\frac{2}{3}\cdot x-\frac{3}{2}\cdot x=\frac{5}{12}\)

\(\left(\frac{2}{3}-\frac{3}{2}\right)\cdot x=\frac{5}{12}\)

\(-\frac{5}{6}\cdot x=\frac{5}{12}\)

\(x=\frac{\frac{5}{12}}{-\frac{5}{6}}\)

\(x=-\frac{1}{2}\)

b) \(\frac{7}{9}:\left(2+\frac{3}{4}\cdot x\right)+\frac{5}{9}=\frac{23}{27}\)

\(\frac{7}{9}:\left(2+\frac{3}{4}\cdot x\right)=\frac{23}{27}-\frac{5}{9}\)

\(\frac{7}{9}:\left(2+\frac{3}{4}\cdot x\right)=\frac{8}{27}\)

\(2+\frac{3}{4}\cdot x=\frac{7}{9}:\frac{8}{27}\)

\(2+\frac{3}{4}\cdot x=2\frac{5}{8}\)

\(\frac{3}{4}\cdot x=2\frac{5}{8}-2\)

\(\frac{3}{4}\cdot x=\frac{5}{8}\)

\(x=\frac{5}{8}:\frac{3}{4}\)

\(x=\frac{5}{6}\)

c) \(\frac{2}{5}+\frac{3}{5}\cdot\left(3x-3.7\right)=-\frac{53}{10}\)

\(\frac{3}{5}\cdot\left(3x-3.7\right)=-\frac{53}{10}-\frac{2}{5}\)

\(\frac{3}{5}\cdot\left(3x-3.7\right)=-5\frac{7}{10}\)

\(3x-3.7=-5\frac{7}{10}:\frac{3}{5}\)

\(3x-3.7=-9\frac{1}{2}\)

\(3x=-9\frac{1}{2}+3.7\)

\(3x=-5.8\)

\(x=\left(-5.8\right):3=-1,9\left(3\right)\)