Question

a) \(\frac{x}{x+4}\) = \(\frac{5}{6}\)

b) \(\frac{x-3}{x+5}\) = \(\frac{5}{7}\)

c) \(\frac{x+4}{20}\) = \(\frac{5}{20}\)

tìm x nha các bạn

Answer 1

a) Ta có:

\(\frac{x}{x+4}=\frac{5}{6}\)

\(\Rightarrow6x=5\left(x+4\right)\)

\(\Rightarrow6x=5x+20\)

\(\Rightarrow5x+20-6x=0\)

\(-x=-20\)

\(x=20\)

b)Ta có:  \(\frac{x-3}{x+5}=\frac{5}{7}\)

\(\Rightarrow7\left(x-3\right)=5\left(x+5\right)\)

\(\Rightarrow7x-21=5x+25\)

\(\Rightarrow7x-21-5x-25=0\)

\(2x=46\)

\(x=23\)

c)Ta có: \(\frac{x+4}{20}=\frac{5}{20}\)

\(\Rightarrow x+4=5\)

\(\Rightarrow x=1\)