D

B

C

C

D

B

\(\dfrac{3}{x}+5=15\%\)

\(\dfrac{3}{x}+5=\dfrac{3}{20}\)

\(\Rightarrow\dfrac{3}{x}=\dfrac{3}{20}-5\)

\(\Rightarrow\dfrac{3}{x}=\dfrac{3}{20}-\dfrac{100}{20}\)

\(\Rightarrow\dfrac{3}{x}=-\dfrac{97}{20}\)

\(\Rightarrow x=\dfrac{-20.3}{97}\)

\(\Rightarrow x=-\dfrac{60}{97}\)

B

C

1KW = 1000W

1 ngày 12 giờ = 36 giờ

\(\dfrac{3}{4}\) phút = \(45\) giây

A. Đ

B. S

C. S

c) \(2\left(\dfrac{1}{2}x-\dfrac{1}{3}\right)-\dfrac{3}{2}=\dfrac{1}{4}\)

\(\Rightarrow2\left(\dfrac{1}{2}x-\dfrac{1}{3}\right)=\dfrac{1}{4}+\dfrac{3}{2}\)

\(\Rightarrow2\left(\dfrac{1}{2}x-\dfrac{1}{3}\right)=\dfrac{1}{4}+\dfrac{6}{4}\)

\(\Rightarrow2\left(\dfrac{1}{2}x-\dfrac{1}{3}\right)=\dfrac{7}{4}\)

\(\Rightarrow\left(\dfrac{1}{2}x-\dfrac{1}{3}\right)=\dfrac{7}{4}:2\)

\(\Rightarrow\left(\dfrac{1}{2}x-\dfrac{1}{3}\right)=\dfrac{7}{4}.\dfrac{1}{2}\)

\(\Rightarrow\left(\dfrac{1}{2}x-\dfrac{1}{3}\right)=\dfrac{7}{8}\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{7}{8}+\dfrac{1}{3}\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{21}{24}+\dfrac{8}{24}\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{29}{24}\)

\(\Rightarrow x=\dfrac{29}{24}:\dfrac{1}{2}\)

\(\Rightarrow x=\dfrac{29}{24}.2\)

\(\Rightarrow x=\dfrac{29}{12}\)

d) \(\dfrac{4}{5}-\dfrac{1}{2}x=\dfrac{1}{10}\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{4}{5}-\dfrac{1}{10}\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{8}{10}-\dfrac{1}{10}\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{7}{10}\)

\(\Rightarrow x=\dfrac{7}{10}:\dfrac{1}{2}\)

\(\Rightarrow x=\dfrac{7}{10}.2\)

\(\Rightarrow x=\dfrac{7}{5}\)

D