7 11/15 - (3 9/20 +1 1/30)

$$7 \frac{11}{15} - (3 \frac{9}{20} + 1 \frac{1}{30}) = 7 \frac{11}{15} - (3 + \frac{9}{20} + 1 + \frac{1}{30}) = 7 \frac{11}{15} - (4 + \frac{9}{20} + \frac{1}{30}) = 7 \frac{11}{15} - (4 + \frac{9 \cdot 3}{20 \cdot 3} + \frac{1 \cdot 2}{30 \cdot 2}) = 7 \frac{11}{15} - (4 + \frac{27}{60} + \frac{2}{60}) = 7 \frac{11}{15} - (4 + \frac{29}{60}) = 7 \frac{11}{15} - 4 - \frac{29}{60} = 3 + \frac{11}{15} - \frac{29}{60} = 3 + \frac{11 \cdot 4}{15 \cdot 4} - \frac{29}{60} = 3 + \frac{44}{60} - \frac{29}{60} = 3 + \frac{44-29}{60} = 3 + \frac{15}{60} = 3 + \frac{1}{4} = 3 \frac{1}{4}$$

Ответ: $$3 \frac{1}{4}$$