Question

решите, пожалуйста (20б)

Answer 1

$\frac{0.1}{y + 7} = \frac{0.9}{y - 6} \\ 0.1(y - 6) = 0.9(y + 7) \\ 0.1y - 0.6 = 0.9y + 6.3 \\ 0.1y - 0.9y = 6.3 + 0.6 \\ - 0.8y = 6.9 \\ y = 6.9 \div ( - 0.8) = \frac{69}{10} \div ( - \frac{8}{10} ) = \frac{69}{10} \times ( - \frac{10}{8} ) = - \frac{69}{8} = - 8 \frac{5}{8}$