Task 1. Represent in the form of an irreducible fraction

$$
6 \frac{3}{2015} \times 8 \frac{11}{2016}-11 \frac{2012}{2015} \times 3 \frac{2005}{2016}-12 \times \frac{3}{2015}
$$
Answer: $11 / 112$.

Solution. First solution. Let $a=3 / 2015, b=11 / 2016$. Then

$$
\begin{aligned}
& 6 \frac{3}{2015} \times 8 \frac{11}{2016}-11 \frac{2012}{2015} \times 3 \frac{2005}{2016}-12 \times \frac{3}{2015}=(6+a)(8+b)-(12-a)(4-b)-12 a= \\
& =48+8 a+6 b+a b-48+4 a+12 b-a b-12 a=18 b=18 \cdot \frac{11}{2016}=\frac{18 \cdot 11}{18 \cdot 112}=\frac{11}{112}
\end{aligned}
$$

Second solution. After replacing the mixed fractions with common fractions, we get that the original expression equals

$$
\begin{gathered}
\frac{12093}{2015} \cdot \frac{16139}{2016}-\frac{24177}{2015} \cdot \frac{8053}{2016}-\frac{36}{2015}=\frac{195168927-194697381-72576}{2015 \cdot 2016}= \\
=\frac{398970}{2015 \cdot 2016}=\frac{2015 \cdot 18 \cdot 11}{2015 \cdot 18 \cdot 112}=\frac{11}{112}
\end{gathered}
$$