8 3 51 17 -- --

$$\frac{8}{51} + \frac{3}{17} = \frac{8}{51} + \frac{3 \cdot 3}{17 \cdot 3} = \frac{8}{51} + \frac{9}{51} = \frac{17}{51} = \frac{1}{3}$$

Ответ: $$\frac{1}{3}$$