\[\boxed{\text{118\ (118).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ 5x - 0,7 < 3x + 5,1\]
\[5x - 3x < 5,1 + 0,7\]
\[2x < 5,8\]
\[x < 5,8\ :2\]
\[x < 2,9.\]
\[Ответ:x < 2,9.\]
\[\textbf{б)}\ 0,8x + 4,5 \geq 5 - 1,2x\]
\[0,8x + 1,2x \geq 5 - 4,5\]
\[2x \geq 0,5\]
\[x \geq 0,5\ :2\]
\[x \geq 0,25.\]
\[Ответ:x \geq 0,25.\]
\[\textbf{в)}\ 2x + 4,2 \leq 4x + 7,8\]
\[2x - 4x \leq 7,8 - 4,2\]
\[- 2x \leq 3,6\]
\[2x \geq - 3,6\]
\[x \geq - 3,6\ :2\]
\[x \geq - 1,8\]
\[Ответ:x \geq - 1,8.\]
\[\textbf{г)}\ 3x - 2,6 > 5,5x - 3,1\]
\[3x - 5,5x > - 3,1 + 2,6\]
\[- 2,5x > - 0,5\]
\[2,5x < 0,5\]
\[x < 0,5\ :2,5\]
\[x < 0,2.\]
\[Ответ:x < 0,2.\]