8) 3+1=

$$3\frac{7}{30}+1\frac{9}{20} = 3\frac{7 \cdot 2}{30 \cdot 2}+1\frac{9 \cdot 3}{20 \cdot 3} = 3\frac{14}{60}+1\frac{27}{60} = 4\frac{41}{60}$$

Ответ: $$4\frac{41}{60}$$