7.

Решение:

\( 1 \frac{9}{16} + 3 \frac{1}{5} - 9 \frac{2}{5} \)

\( \frac{25}{16} + \frac{16}{5} - \frac{47}{5} = \frac{25}{16} - \frac{31}{5} = \frac{25 \cdot 5 - 31 \cdot 16}{80} = \frac{125 - 496}{80} = \frac{-371}{80} \)

\( 12 \frac{2}{3} - 61 \frac{1}{2} : 6 \frac{3}{4} \)

\( 12 \frac{2}{3} = \frac{38}{3} \)

\( 61 \frac{1}{2} = \frac{123}{2} \)

\( 6 \frac{3}{4} = \frac{27}{4} \)

\( \frac{123}{2} : \frac{27}{4} = \frac{123}{2} \cdot \frac{4}{27} = \frac{123 \cdot 2}{27} = \frac{41 \cdot 2}{9} = \frac{82}{9} \)

\( \frac{38}{3} - \frac{82}{9} = \frac{38 \cdot 3 - 82}{9} = \frac{114 - 82}{9} = \frac{32}{9} \)

\( 17 \frac{7}{12} - 6 \frac{1}{3} \)

\( 17 \frac{7}{12} = \frac{204 + 7}{12} = \frac{211}{12} \)

\( 6 \frac{1}{3} = \frac{19}{3} \)

\( \frac{211}{12} - \frac{19}{3} = \frac{211 - 19 \cdot 4}{12} = \frac{211 - 76}{12} = \frac{135}{12} = \frac{45}{4} \)

\( 2 \frac{2}{3} \)

Решаем верхний пример:

\( \frac{-371}{80} + \frac{32}{9} = \frac{-371 \cdot 9 + 32 \cdot 80}{720} = \frac{-3339 + 2560}{720} = \frac{-779}{720} \)

Решаем второй пример:

\( \frac{45}{4} + 2 \frac{2}{3} = \frac{45}{4} + \frac{8}{3} = \frac{45 \cdot 3 + 8 \cdot 4}{12} = \frac{135 + 32}{12} = \frac{167}{12} \)

Ответ: Верхний пример \( \frac{-779}{720} \), Нижний пример \( \frac{167}{12} \).