4. Выполните действия: а) 1-1: 16-18; в) 5-23; г) 4-3

a) $$1 - \frac{1}{13} = \frac{13}{13} - \frac{1}{13} = \frac{13 - 1}{13} = \frac{12}{13}$$.

б) $$16 - \frac{11}{18} = \frac{16 \cdot 18}{18} - \frac{11}{18} = \frac{288}{18} - \frac{11}{18} = \frac{288 - 11}{18} = \frac{277}{18} = 15\frac{7}{18}$$.

в) $$5 - 2\frac{3}{4} = 5 - \frac{2 \cdot 4 + 3}{4} = 5 - \frac{8 + 3}{4} = 5 - \frac{11}{4} = \frac{5 \cdot 4}{4} - \frac{11}{4} = \frac{20}{4} - \frac{11}{4} = \frac{20 - 11}{4} = \frac{9}{4} = 2\frac{1}{4}$$.

г) $$4 - 3\frac{1}{13} = 4 - \frac{3 \cdot 13 + 1}{13} = 4 - \frac{39 + 1}{13} = 4 - \frac{40}{13} = \frac{4 \cdot 13}{13} - \frac{40}{13} = \frac{52}{13} - \frac{40}{13} = \frac{52 - 40}{13} = \frac{12}{13}$$.

Ответ: а) $$\frac{12}{13}$$; б) $$15\frac{7}{18}$$; в) $$2\frac{1}{4}$$; г) $$\frac{12}{13}$$