\[\boxed{\text{465\ (465).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ \frac{4}{5} = \frac{8}{10} = 0,8;\]
\[2)\ \frac{3}{8} = \frac{375}{1000} = 0,375;\]
\[3)\ \frac{7}{16} = \frac{4375}{10000} = 0,4375;\]
\[4)\ \frac{97}{80} = 1\frac{17}{80} = 1\frac{2125}{10000} =\]
\[= 1,2125;\]
\[5)\ \frac{42}{15} = 2,8.\ \]
\[\boxed{\text{4}\text{6}\text{5}\text{.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[1)\ A = \left\{ 2,\ 7,\ 8 \right\};\ \ B = \{ 3,\ 5,\ 6,\ 8\}\]
\[\ \ A \cup B = \left\{ 2,\ 3,\ 5,\ 6,\ 7,\ 8 \right\};\]
\[2)\ A = \left\{ 5 \right\},;\ B = \{ 7\}\]
\[\ \ A \cup B = \left\{ 5,\ 7 \right\}.\ \]