ГДЗ по алгебре 7 класс Макарычев Задание 674

\[\boxed{\text{674\ (674).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ \frac{3x - 5}{2} + \frac{8x - 12}{7} = 9\ \ \ | \cdot 14\]

\[7 \cdot (3x - 5) + 2 \cdot (8x - 12) =\]

\[= 9 \cdot 14\]

\[21x - 35 + 16x - 24 = 126\]

\[37x = 126 + 59\]

\[37x = 185\]

\[x = 5\]

\[Ответ:x = 5.\]

\[\textbf{б)}\ \frac{21 - 4x}{9} - \frac{8x + 15}{3} = 2\ \ \ | \cdot 9\]

\[21 - 4x - 3 \cdot (8x + 15) = 18\]

\[21 - 4x - 24x - 45 = 18\]

\[- 28x = 18 + 24\]

\[- 28x = 42\]

\[x = 42\ :( - 28) = - \frac{42}{28} = - \frac{3}{2}\]

\[x = - 1,5\ \]

\[Ответ:x = - 1,5.\]