\[\left( 5,4 \cdot 3\frac{1}{3} + 13,8 \right)\ :1\frac{13}{15} + 3\frac{5}{6} =\]
\[= \left( \frac{54}{10} \cdot \frac{10}{3} + 13,8 \right)\ :\frac{28}{15} + 3\frac{5}{6} =\]
\[= (18 + 13,8) \cdot \frac{15}{28} + 3\frac{5}{6} =\]
\[= 31,8 \cdot \frac{15}{28} + 3\frac{5}{6} =\]
\[= \frac{318}{10} \cdot \frac{15}{28} + 3\frac{5}{6} =\]
\[= \frac{159}{5} \cdot \frac{15}{28} + 3\frac{5}{6} = \frac{477}{28} + 3\frac{5}{6} =\]
\[= 17\frac{1^{\backslash 3}}{28} + 3\frac{5^{\backslash 14}}{6} =\]
\[= 17\frac{3}{84} + 3\frac{70}{84} = 20\frac{73}{84}.\]