3 : 3 3/4 + 2 2/5 * 2 1/2 - 3 5/6 По действиям спасибо.

1) $3:3\frac{3}{4}=3:\frac{15}{4}=3*\frac{4}{15}=\frac{4}{5};$
2) $2\frac{2}{5}*2\frac{1}{2}=\frac{12}{5}*\frac{5}{2}=\frac{6}{1}*\frac{1}{1}=6;$
3) $3\frac{5}{6}=\frac{23}{6};$
4) $\frac{4}{5}+6=\frac{4}{5}+5\frac{5}{5}=\frac{4}{5}+\frac{30}{5}=\frac{34}{5};$
5) $\frac{34}{5}-\frac{23}{6}=\frac{204}{30}-\frac{115}{30}=\frac{89}{30}=2\frac{29}{30}.$