5:15 19

$${\frac{5}{19}} : 15 = {\frac{5}{19}} \cdot {\frac{1}{15}} = {\frac{5}{19 \cdot 15}} = {\frac{5}{19 \cdot 5 \cdot 3}} = {\frac{1}{19 \cdot 3}} = {\frac{1}{57}}$$

Ответ: $$\frac{1}{57}$$