Решите уравнение: корень из (9-20x)=7.

\[\sqrt{9 - 20x} = 7\]

\[9 - 20x > 0\]

\[- 20x > - 9\]

\[20x < 9\]

\[x < \frac{9}{20} < 0,45.\]

\[9 - 20x = 7\]

\[- 20x = - 2\]

\[x = \frac{2}{20} = 0,1 < 0,45.\]

\[Ответ:x = 0,1.\]