Решение:

$$\frac{3\frac{4}{15}\cdot\frac{5}{9}}{\frac{3}{4}:0,75-(3-\frac{1}{15})\cdot\frac{4}{13}:2,5}$$ = $$\frac{\frac{49}{15}\cdot\frac{5}{9}}{\frac{3}{4}:\frac{3}{4}-(\frac{45}{15}-\frac{1}{15})\cdot\frac{4}{13}:\frac{5}{2}}$$ = $$\frac{\frac{49}{27}}{\frac{3}{4}\cdot\frac{4}{3}-\frac{44}{15}\cdot\frac{4}{13}\cdot\frac{2}{5}}$$ = $$\frac{\frac{49}{27}}{1-\frac{352}{975}}$$ = $$\frac{\frac{49}{27}}{\frac{623}{975}}$$ = $$\frac{49}{27}\cdot\frac{975}{623}$$ = $$\frac{49\cdot325}{9\cdot623}$$ = $$\frac{15925}{5607}$$ $$
eq$$ 0

Ответ: Дробь не равна нулю и имеет смысл.