3. Решите уравнение: a) $$5,23+x= -7,24$$; б) $$y-2\frac{5}{12}=-3\frac{7}{15}$$.

Решение: a) $$5,23 + x = -7,24$$ $$x = -7,24 - 5,23$$ $$x = -12,47$$ б) $$y - 2\frac{5}{12} = -3\frac{7}{15}$$ $$y = -3\frac{7}{15} + 2\frac{5}{12}$$ $$y = -\frac{3 \cdot 15 + 7}{15} + \frac{2 \cdot 12 + 5}{12}$$ $$y = -\frac{45 + 7}{15} + \frac{24 + 5}{12}$$ $$y = -\frac{52}{15} + \frac{29}{12}$$ $$y = -\frac{52 \cdot 4}{15 \cdot 4} + \frac{29 \cdot 5}{12 \cdot 5}$$ $$y = -\frac{208}{60} + \frac{145}{60}$$ $$y = \frac{-208+145}{60}$$ $$y = -\frac{63}{60}$$ $$y = -\frac{21}{20}$$ $$y = -1\frac{1}{20}$$ Ответ: a) $$x=-12,47$$; б) $$y = -1\frac{1}{20}$$