a) \(\frac{x}{5}=\frac{x}{-1}\)
\(\Leftrightarrow\) -x = 5x
\(\Leftrightarrow\) -x - 5x = 0
\(\Leftrightarrow\) -6x = 0
\(\Leftrightarrow\) x = 0
b) \(\frac{3\left(x-1\right)}{-5}\) = \(\frac{4\left(x+2\right)}{6}\)
\(\Leftrightarrow\) \(\frac{-18\left(x-1\right)}{30}\) = \(\frac{-20\left(x+2\right)}{30}\)
\(\Leftrightarrow\) -18(x - 1) = -20(x +2)
\(\Leftrightarrow\) -18x + 18 = -20x - 40
\(\Leftrightarrow\) -18x + 20x = -40 - 18
\(\Leftrightarrow\) 2x = -58
\(\Leftrightarrow\) x = -29
c) \(\frac{7-2x}{3}\) = \(\frac{0,75-5}{4}\)
\(\Leftrightarrow\) (7 - 2x).4 = (0,75 - 5).3
\(\Leftrightarrow\) 28 - 8x = 2,25 - 15
\(\Leftrightarrow\) -8x = -2,25 - 15 - 28 = -40,75
\(\Leftrightarrow\) x = \(\frac{163}{32}\)