Question

tìm x

\(\frac{3}{x+5}=15\%\)    

\(\frac{x}{3}-\frac{10}{21}=\frac{-1}{7}\)

x-25%x=\(\frac{1}{2}\)

 

Answer 1

a)

\(\Rightarrow\)X + 5 = 3 : 0,15% = 20

\(\Rightarrow\)X = 20 - 5 = 15

Vậy X = 15

b) 

\(\Rightarrow\)\(\frac{7x}{21}\) - \(\frac{10}{21}\)= \(\frac{-3}{21}\)

\(\Rightarrow\) \(\frac{7x}{21}\)= \(\frac{-3}{21}\) + \(\frac{10}{21}\)= \(\frac{7}{21}\)

\(\Rightarrow\) 7x = 7 

\(\Rightarrow\) x = 7 : 7 = 1

Vậy X = 1

c)

\(\Rightarrow\)X(1-25%) = \(\frac{1}{2}\)

\(\Rightarrow\)X x 75% = \(\frac{1}{2}\)

\(\Rightarrow\)X = \(\frac{1}{2}\): 75 % = \(\frac{2}{3}\)