$$13\frac{3}{4} = \frac{13 * 4 + 3}{4} = \frac{52 + 3}{4} = \frac{55}{4}$$ $$12\frac{13}{14} = \frac{12 * 14 + 13}{14} = \frac{168 + 13}{14} = \frac{181}{14}$$
$$\frac{55}{4} - \frac{181}{14} = \frac{55 * 7}{4 * 7} - \frac{181 * 2}{14 * 2} = \frac{385}{28} - \frac{362}{28} = \frac{385 - 362}{28} = \frac{23}{28}$$
$$5,6 * \frac{23}{28} = \frac{56}{10} * \frac{23}{28} = \frac{56 * 23}{10 * 28} = \frac{2 * 23}{10} = \frac{46}{10} = 4,6$$
$$2,4 + 4,6 = 7$$
Ответ: 7