1) \(2\frac{1}{2} + 1\frac{1}{4} = \frac{5}{2} + \frac{5}{4} = \frac{10}{4} + \frac{5}{4} = \frac{15}{4}\)
Умножаем на 4: \(4 \cdot \frac{15}{4} = 15\)
2) \(6\frac{2}{3} + 4\frac{4}{5} = \frac{20}{3} + \frac{24}{5} = \frac{20 \cdot 5 + 24 \cdot 3}{15} = \frac{100 + 72}{15} = \frac{172}{15}\)
Делим на 2: \(\frac{172}{15} : 2 = \frac{172}{15} \cdot \frac{1}{2} = \frac{86}{15}\)
3) Вычитаем: \(15 - \frac{86}{15} = \frac{15 \cdot 15 - 86}{15} = \frac{225 - 86}{15} = \frac{139}{15} = 9\frac{4}{15}\)
Ответ: \(9\frac{4}{15}\)