3. Решите уравнение: a) 4,31 - x = 5,18; б) y + 1 1/21 = -2 11/14.

a) $$4,31 - x = 5,18$$ $$-x = 5,18 - 4,31$$ $$-x = 0,87$$ $$x = -0,87$$ Ответ: **-0,87** б) $$y + 1\frac{1}{21} = -2\frac{11}{14}$$ $$y = -2\frac{11}{14} - 1\frac{1}{21}$$ $$y = -2\frac{33}{42} - 1\frac{2}{42}$$ $$y = -3\frac{35}{42}$$ $$y = -3\frac{5}{6}$$ Ответ: **-3 5/6**