4. |5 4/7 − 3 1/2| + |−0,3|.

\(5\frac{4}{7}-3\frac{1}{2}=\frac{39}{7}-\frac{7}{2}=\frac{78-49}{14}=\frac{29}{14}\), поэтому \(\left|5\frac{4}{7}-3\frac{1}{2}\right|=\frac{29}{14}\).

\(|-0.3|=0.3=\frac{3}{10}\).

\(\frac{29}{14}+\frac{3}{10}=\frac{145}{70}+\frac{21}{70}=\frac{166}{70}=\frac{83}{35}=2\frac{13}{35}\).

Ответ: \(\frac{83}{35}\).