Task 1. Represent in the form of an irreducible fraction

$$
6 \frac{7}{2015} \times 4 \frac{5}{2016}-7 \frac{2008}{2015} \times 2 \frac{2011}{2016}-7 \times \frac{7}{2015}
$$
Answer: $5 / 144$.

Solution. First solution. Let $a=7 / 2015, b=5 / 2016$. Then

$$
\begin{aligned}
& 6 \frac{7}{2015} \times 4 \frac{5}{2016}-7 \frac{2008}{2015} \times 2 \frac{2011}{2016}-7 \times \frac{7}{2015}=(6+a)(4+b)-(8-a)(3-b)-7 a= \\
& =24+4 a+6 b+a b-24+3 a+8 b-a b-7 a=14 b=14 \cdot \frac{5}{2016}=\frac{14 \cdot 5}{14 \cdot 144}=\frac{5}{144}
\end{aligned}
$$

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

$$
\begin{gathered}
\frac{12097}{2015} \cdot \frac{8069}{2016}-\frac{16113}{2015} \cdot \frac{6043}{2016}-\frac{49}{2015}=\frac{97610693-97370859-98784}{2015 \cdot 2016}= \\
=\frac{141050}{2015 \cdot 2016}=\frac{2015 \cdot 14 \cdot 5}{2015 \cdot 14 \cdot 144}=\frac{5}{144}
\end{gathered}
$$