1: x=-2/4+3/4=1/4
4: \(\Leftrightarrow\dfrac{x}{5}=\dfrac{6}{30}=\dfrac{1}{5}\)
hay x=1
7: \(\Leftrightarrow\dfrac{x}{15}=\dfrac{-1}{15}\)
nên x=-1
10: \(\Leftrightarrow x=\dfrac{4}{27}-\dfrac{6}{15}=-\dfrac{34}{135}\)
13: \(\Leftrightarrow x=\dfrac{4}{5}+\dfrac{6}{20}-\dfrac{7}{3}=-\dfrac{37}{30}\)
